Concrete compositions comprising activator admixtures for enhancing binding of limestone

Abstract

The present disclosure relates to limestone-containing concrete compositions comprising cementitious material and an activator admixture. The invention provides compositions and methods for producing limestone-containing concrete systems in which limestone is activated within the binder matrix, enabling reduced Portland cement content while maintaining or improving compressive strength and workability. The compositions may be combined with other supplementary cementitious materials, including fly ash and natural pozzolans. By facilitating greater effective utilisation of limestone and supplementary materials, the compositions support a reduction in cement usage and associated carbon emissions.

Description

CONCRETE COMPOSITIONS COMPRISING ACTIVATOR ADMIXTURES FOR ENHANCING BINDING OF LIMESTONETECHNICAL FIELD

[0001] The present disclosure relates to activator admixtures for preparing concrete. These activators are formulated for use in minimal dosages within a concrete mix, yet they elicit substantial improvements in the resulting concrete's properties. In particular embodiments, the activator admixture is combined with materials such as limestone to augment their binding effect within a concrete composition and result in better performance.BACKGROUND

[0002] Cement is a widely used construction material, which is produced by grinding clinker, gypsum, and other mineral additives. While cement production is a vital component of the construction industry, it comes with significant environmental challenges, in particular related to carbon emissions. Cement production is a major contributor to global CO2 emissions. The primary source of CO2 emissions in cement production is the chemical reaction involved in converting limestone (calcium carbonate) into lime (calcium oxide) during the process known as calcination. This process releases CO2 as a byproduct, accounting for around 50% of the total emissions associated with cement production. As well as direct emissions, cement manufacturing also requires substantial energy inputs. The processes involved demand a significant amount of energy, primarily derived from fossil fuels. For example, quarrying raw materials, crushing, grinding, and heating them to high temperatures.

[0003] There is a growing desire to replace at least a portion of the cement used in concrete production with alternative materials that maintain concrete properties while reducing its carbon footprint. Pozzolans, both natural and synthetic, are widely used for this purpose. Pozzolans react with calcium hydroxide and water to form cementitious materials, enhancing the strength and durability of concrete.

[0004] The pozzolanic reaction involves the combination of silicon and aluminium from the pozzolan with available calcium to produce calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH). These compounds improve the mechanical properties of concrete by continuously developing reaction products, resulting in enhanced compressive strength, reduced permeability, and improved chemical resistance.

[0005] Despite their benefits, pozzolanic materials have limitations, including delayed strength development and reduced workability of fresh concrete, which create challenges for their widespread use.

[0006] Cement clinker, commonly referred to as Portland cement clinker, is a solid material that serves as the key intermediate in the manufacture of Portland cement. It isformed by heating a carefully proportioned mixture of raw materials, primarily limestone (calcium carbonate), along with other minerals, such as clay or shale, at approximately 1400°C in a rotary kiln. During this high-temperature process, chemical transformations occur, including the decarbonation of limestone and the formation of hydraulic phases.

[0007] The resultant clinker consists of nodules that are subsequently ground with gypsum to produce Portland cement. The addition of gypsum regulates the setting time of the cement. Limestone plays a dual role in this process, acting as a source of calcium for the formation of clinker phases and as a grinding additive when mixed with gypsum. The use of limestone in cement production is essential for achieving the desired binding and performance properties in cementitious materials.

[0008] Despite its importance in the production of clinker, limestone is not typically used as an additive to cement in producing concrete. This is because limestone is generally considered to have limited direct binding properties when added to concrete on its own, i.e. it is considered to be a "filler". Unlike cement, which undergoes hydration reactions to form calcium silicate hydrate (C-S-H) and other binding phases, limestone primarily acts as an inert filler in the concrete matrix. Its contribution is largely physical rather than participating significantly in chemical reactions that enhance strength or durability.

[0009] Additionally, the presence of excessive limestone in concrete can reduce its mechanical strength due to the dilution of the cementitious binder, limiting its application as an active additive. Portland Limestone Cement (PLC), also known as Type IL cement, has gained popularity globally due to its environmental benefits and performance parity with traditional Portland cement. PLC comprises finely ground limestone typically at 5-15% substitution of clinker which reduces the carbon footprint of the final cement product. This reduction stems from decreased clinker content, leading to lower carbon dioxide emissions during production.

[0010] The use of PLC introduces several challenges that require careful consideration. PLC may exhibit reduced early-age strength compared to Ordinary Portland Cement (OPC) due to slower hydration rates. This can be particularly critical in applications that require rapid setting and early strength gain. Some studies have also suggested that PLC has compromised durability properties and reduced later-age strength, which could limit its suitability for certain structural applications. Further, the addition of limestone in PLC can alter the setting characteristics of concrete, often resulting in longer setting times compared to OPC. This can impact construction schedules and require adjustments to mix designs. PLC mixtures also have increased water demand and decreased workability, leading to mixes that are difficult to place and finish. Although PLC can enhance certain durability properties, excessive limestone content may increase porosity and reduce resistance to aggressive chemical environments, such as sulphates or acids. In harsh or chemically active environments, this compromises the long-term durability of concrete structures.

[0011] To address these challenges, the inventors have developed activator admixtures for use in concrete comprising limestone or other fillers. These admixtures activate pozzolans and fillers, enabling rapid strength development, improved workability, and enhanced durability. They enable the use of limestone as a substitute for a portion of OPC typically required.

[0012] In light of the above, there is a need for activator admixtures tailored to address the specific issues posed by using limestone as a cement substitute in concrete production. The present invention at least partially addresses this need by providing activators and methods that augment the binding performance and workability of concrete compositions comprising limestone, including PLC. These advancements enable the production of high-quality, durable concrete with a lower environmental impact, paving the way for wider adoption of sustainable construction practices.

[0013] In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

[0014] It is an object of the invention to provide activators for concrete to enable enhanced strength, workability and / or durability, concrete compositions comprising the activators, and related methods of use and production, that overcome or ameliorate at least one of the disadvantages of the prior art. Alternatively, it is an object of the invention to provide the public with a useful choice.SUMMARY OF THE INVENTION

[0015] The present invention relates to a novel concrete composition in which a portion of cementitious material may be replaced with limestone while maintaining or improving the mechanical properties, durability, and workability of the concrete. The invention further provides an activator admixture comprising a pozzolan component, which may enhance cement hydration and optimise performance in the presence of limestone.

[0016] A concrete composition comprising an activator admixture, cementitious material, and limestone, wherein the activator admixture comprises a pozzolan component, the pozzolan component comprising a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

[0017] The limestone may replace up to 30% by weight of the cementitious material, and in some examples, it may be present in varying replacement levels such as 5-15%, 15-25%, or 25-30% by weight of the cementitious material. The limestone may be selected from natural limestone, processed limestone, ground limestone, or precipitated calciumcarbonate. In some examples, it may comprise at least 90% calcium carbonate (CaCOs). The limestone may further be provided with a controlled median particle size, which may range from 1-150 pm to optimise its interaction with the cementitious matrix.

[0018] In another example, there is provided an activator admixture that may improve the mechanical and chemical properties of concrete compositions comprising limestone. The activator pozzolan component may comprise silicon dioxide (SiCb) in the range of 20-80% w / w and aluminium oxide (AI2O3) in the range of 5-40% w / w. In some examples, the pozzolan component may comprise 40-80% SiO2 and 10-40% AI2O3. The pozzolan component may include at least two pozzolan portions with different particle sizes, where the first pozzolan portion may have an intermediate median particle size of 0.5-1.5 pm, and the second pozzolan portion may have a coarse median particle size of 10-80 pm. The activator admixture may be electrostatically charged, and the charge may be applied using external electrical or electrostatic fields generated by electrodes, electrostatic spraying techniques, triboelectric charging in a fluidised bed, corona discharge methods, electrostatic fluidisation, or mechanical mixing-induced friction.

[0019] The activator admixture may be formulated as a powdered admixture and may optionally include a plasticiser. The plasticiser, may be included in an amount of 8-40% w / w, or in some examples, 10-25% w / w or 10-35% w / w, depending on the desired workability. The plasticiser may be selected from: Polycarboxylate plasticisers, Naphthalene-based plasticisers, Lignosulphonate plasticisers, Dry powder plasticisers, and Dry powder polycarboxylate plasticisers.

[0020] The plasticiser may optionally have a Dv50 of 50-500 pm, and in some examples, a Dv50 of 100-200 pm. The pozzolan-to-plasticiser ratio may be from 9:1 to 3:1, or from 11:1 to 1.5:1, optimising its dispersion within the concrete composition.

[0021] In one example, a concrete composition comprises a cementitious material, limestone, and an activator admixture, wherein the activator admixture enhances the compressive strength of the concrete composition compared to a corresponding composition containing limestone but without the activator admixture.

[0022] In some examples, the activator admixture comprises at least two pozzolan portions with distinct chemical compositions and / or particle size distributions, optimising hydration reactions and improving microstructural development.

[0023] In one example, the activator admixture facilitates increased hydration, densification of the concrete matrix, and improved long-term strength, compensating for the reduction in cement content associated with limestone replacement.

[0024] In some examples, the activator admixture improves early and long-term compressive strength, providing a measurable increase at 1, 3, 7, 28, or 56 days compared to a limestone-containing concrete composition without the activator admixture.

[0025] In one example, the activator admixture enables at least a 10% increase in compressive strength at any one of day 1, 3, 7, 28 or 56 compared to a limestonecontaining concrete composition without the activator admixture.

[0026] In some examples, the activator admixture improves early strength development, providing at least a 10% increase in compressive strength at 1 or 3 days compared to a limestone-containing concrete composition without the activator admixture.

[0027] In one example, the activator admixture may be electrostatically charged to improve reactivity and dispersion of the pozzolan portions within the cementitious system, further enhancing hydration efficiency.

[0028] In some examples, the activator admixture promotes the formation of additional calcium-silicate-hydrate (C-S-H) phases, increasing the interaction between limestone and cement hydration products, thereby improving mechanical properties and durability.

[0029] In one example, the activator admixture allows for the replacement of up to 30% of the cementitious material with limestone while maintaining or improving compressive strength compared to a limestone-containing concrete composition without the activator admixture.

[0030] In some examples, the invention provides an efficient method for producing high-performance limestone-containing concrete, reducing reliance on clinker while ensuring superior structural performance and sustainability.

[0031] In another example, there is provided a cementitious composition comprising limestone, activator admixture and supplementary cementitious materials (SCMs). The cementitious materials may comprise Portland cement and at least one SCM selected from fly ash, slag, silica fume, metakaolin, rice husk ash, synthetic pozzolan, natural pozzolan, and pumice. The SCM may be present in an amount of 10-50% w / w of the cementitious material. It may be wholly or partially substituted by limestone (up to 100% of the SCM replacement). The composition may optionally comprise cement at levels below 50%, 60%, 70%, 80%, or 90% by weight of the cementitious material, thereby offering a more sustainable alternative to conventional cement-based concrete.

[0032] In one example, a concrete composition comprises a cementitious material, limestone, and a supplementary cementitious material (SCM), wherein the limestone and SCM are present in a 1:1 ratio, and the activator admixture enhances their combined reactivity to maintain or improve compressive strength compared to a corresponding composition without the activator admixture.

[0033] In some examples, the concrete composition includes limestone and SCM in a 2:1 ratio. In this example the higher limestone content is balanced by the activator admixture to provide increased strength at day 1, 3 or 7.

[0034] In one example, the concrete composition contains limestone and SCM in a 1:2 ratio.

[0035] In one example, the activator admixture enhances the interaction between SCM and limestone, promoting additional calcium-silicate-hydrate (C-S-H) formation and improving cementitious efficiency regardless of the limestone-to-SCM ratio.

[0036] In some examples, the limestone-to-SCM ratio is optimised based on performance requirements, with higher limestone levels (e.g., 2:1) improving workability and early strength, while higher SCM levels (e.g., 1:2) contribute to long-term strength and durability.

[0037] In one example, the activator admixture allows for up to 50% replacement of cementitious material with a combination of limestone and SCMs, maintaining comparable or superior strength to a reference composition without the activator admixture.

[0038] In some examples, the activator admixture modifies the hydration process to ensure compatibility across different limestone-to-SCM ratios, enabling consistent strength development and durability performance in both standard and high-performance concrete applications.

[0039] The activator admixture may exhibit a controlled particle size distribution, which may be defined by:a. 55% of particles being less than 15 pm;b. 50-80% of particles being less than 40 pm; andc. 70-100% of particles being less than 90 pm.

[0040] In some examples, the specific surface area (SSA) of the activator admixture may be between 350-1000 m2 / kg. The Dv50 of the activator admixture may be less than 40 pm, and in some examples, it may range between 10-50 pm. The activator may exhibit a first volume density peak of between 0.3 and 1.5% for particles at 0.5-1.5 pm, and a second volume density peak of greater than 3% between 10-80 pm. The activator may exhibit for these volume density peaks a ratio of 1:3 to 1:6.

[0041] The concrete composition provided may exhibit improved performance characteristics, including a compressive strength of at least 20 MPa at 28 days, optionally 25MPA, or 30MPa as determined by NZS 3112 Part 2. The formulation may allow for enhanced cement efficiency and contribute to carbon footprint reduction by reducing reliance on Portland cement.

[0042] In some examples, the activator admixture may be present in a concrete composition at between 0.25-10% of cementitious materials. In some examples, the activator admixture may be present in a concrete composition at between 0.5-8% ofcementitious materials. In some examples, the activator admixture may be present in a concrete composition at between 1-4% of cementitious materials.

[0043] In another example, there is provided a concrete structure formed from the concrete composition.

[0044] In yet another example, there is provided a method of producing the concrete composition, comprising the steps of:a) Obtaining a first pozzolan portion with a first chemical composition and a second pozzolan portion with a second chemical composition;b) Combining the first and second pozzolan portions to form a pozzolan component; c) Mixing the pozzolan component with a plasticiser to produce an activator admixture; d) Combining the activator admixture with cementitious material and limestone; wherein the pozzolan component comprises 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.

[0045] In yet another example, there is provided a method of producing a limestone concrete composition comprising:a) obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b) combining the first and second pozzolan portions to form a pozzolan component; and c) combining cementitious material, limestone, water, and an activator admixture comprising the pozzolan component and a plasticiser to form the limestone concrete composition,wherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0046] The method may optionally include electrostatically charging the activator admixture using any of the methods described above. In some examples, the pozzolan and plasticiser may be mixed for at least five minutes before addition to the cementitious mixture.

[0047] Additionally, the concrete composition may develop a compressive strength of at least 25 MPa at 28 days and may contain at least 10% by weight of natural or synthetic pozzolan SCM as a cement substitute.

[0048] There is provided an improved cementitious composition and production method, which enables partial cement replacement with limestone while maintaining or enhancing the strength, durability, and sustainability of concrete.

[0049] In another example there is provided a method of increasing limestone reactivity in a limestone concrete composition comprising limestone and cementitious material, the method comprising adding an activator admixture, to the cementitious material and limestone. The activator admixture may be as described in any one or more of the Clauses. In one example the method promotes formation of calcium-silicate-hydrate and / or carboaluminate hydration phases.

[0050] Those of skill in the art will appreciate that the examples, features, variations and embodiments described in relation to any of the aspects herein are intended to be read in combination with the features of any other aspect or example provided herein, regardless of whether such examples, features, variations and embodiments are specifically appended to said aspects or examples.

[0051] Aspects of the invention may also be said broadly to consist in the examples, parts, elements and features referred to or indicated in this specification, individually or collectively, in any or all combinations of two or more of said parts, elements or features, and where specific integers are mentioned herein that have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0052] Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Embodiments will now be described by way of example only and with reference to the figures:Figure l.a.i - Comparison of strength over time for activator versus control concrete.Figure l.a.ii - Particle size and volume density of particles for activator gamma.Figure l.a.iii - Particle size and volume density of particles for activator omicron.Figure l.b.i - Slump loss of concrete over time for control and activator-containing concrete.Figure l.b.ii - Comparison of strength over time for activator versus control concrete showing that the activators produced concrete with higher compressive strength at all time points. Data for day 28 still to come.Figure l.b.iii - Particle size and volume density of particles for activator Tau.Figure l.b.iv - Particle size and volume density of particles for activator Omega2.Figure l.c.i - Slump loss of concrete over time showing that workability of control 2 and activator retained workability to a similar extent.Figure l.c.ii - Comparison of strength over time for 25MPa concrete, 40MPa concrete, and activator-containing concrete using 25MPa concrete's cement volume with strength at 1, 3, 7 and 28 days post-pour.Figure l.c.iii - Particle size and volume density of particles for activator Pi.Figure 2.a.i - Slump loss of concrete over time showing good workability for all activatorcontaining concrete mixtures.Figure 2.a.ii - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete at all cement-reduction levels had compressive strength substantially equal to or greater than control at 1, 3, 7 and 28 days post-pour. Figure 2. a . iii - Particle size and volume density of particles for activator Pi.Figure 2.a.iv - Particle size and volume density of particles for activator Tau.Figure 2.b.i - Slump loss of activator-containing concrete over time showing significant improvement in workability vs. both controls.Figure 2. b. ii - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete with 50% less cement produced compressive strength greater than controls 1 and 2 at all tested ages - 1, 3, 7 and 28 days post-pour. Figure 2. b. iii - Particle size and volume density of particles for activator Tau.Figure 3 - Comparison of strength over time for KNP activated natural pozzolans vs control and Activator activated pozzolans vs. control, both at 20% cement replacement levels. Figure 4 - Particle size and volume density of particles for activator Pi.Figures 5A-5C show volume density of particle size classes of activators of the invention in example 5.Figure 5D shows compressive strength over time for mortar mixes from example 5.Figures 6A shows volume density of particle size classes of an activator of the invention according to example 6.Figure 6B shows compressive strength over time for mortar mixes of example 6.Figure 7 shows compressive strength over time for mortar mixes of example 7.Figure 8 shows compressive strength over time for mortar mixes of example 8.Figure 9A and 9B show exemplary concrete compositions prepared using 9A ordinary Portland cement and 9B activator admixtures of the invention.Figure 10 shows compressive strength over time for activators of the invention.Figure 11 shows the effect of activator admixtures when added to limestone and supplementary cementitious materials in a concrete composition.Figure 12 shows the effect of activator admixtures when added to limestone in a concrete composition.Figure 13 shows the effect of an activator admixture in a 100% cement concrete composition, by reference to compressive strength development over time.Figure 14 shows the effect of an activator admixture when added to a concrete composition comprising 30% limestone cement replacement, by reference to compressive strength development over time.Figure 15 shows the effect of an activator admixture when added to a concrete composition comprising 20% limestone and 10% fly ash cement replacement by reference to compressive strength development over time.Figure 16 shows the effect of an activator admixture when added to a concrete composition comprising 20% limestone and 10% Pl cement replacement, by reference to compressive strength development over time.Figure 17 shows the particle size distribution and cumulative volume density of particles for activator K4e and activator A+.DETAILED DESCRIPTION OF THE INVENTION

[0054] Unless the context clearly indicates otherwise, terms used herein are defined as follows:

[0055] "Comprising" means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise", include", "including" and "comprises" are to be interpreted in the same manner.

[0056] "A" or "an" does not exclude a plurality.

[0057] "About" as used herein means a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, when applied to a value, the term should be construed as including a deviation of + / - 5% of the value.

[0058] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical valuesbetween the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

[0059] Whenever a range is given in the specification, for example, a dimensional range, a time range, or a composition range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure.

[0060] "And / or" means additionally or alternatively. Moreover, any use of a term in the singular also encompasses plural forms.

[0061] "Particle(s)" refers to particles having a well-defined physical shape as well as those with irregular geometries, including any particles having the physical shape of platelets, shavings, fibers, flakes, ribbons, rods, strips, spheroids, toroids, pellets, tablets, or any other physical shape.

[0062] "Cement" includes Portland cement and similar materials that contain one or more of the four clinker materials: C3S (tricalcium silicate), C2S (dicalcium silicate), C3A (tricalcium aluminate), and C4AF (tetracalcium aluminoferrite).

[0063] "Concrete activator", "activator", or "activator admixture" means a mixture of components for adding to concrete mixtures which modifies the reaction speed or curing process when the activator is added to a concrete mix.

[0064] "Cementitious material" means the total quantity of hydraulically reactive binder material in the composition and comprises Portland cement and optionally one or more supplementary cementitious materials (SCMs). The term does not include aggregate, filler, water, limestone replacement material, or activator admixture (including any pozzolan component or plasticiser thereof) unless expressly stated. Unless otherwise specified, any percentage expressed relative to the cementitious material (for example, where the activator admixture is present in an amount of 0.25-10%, optionally 0.5-8%, optionally 1-4% by weight of cementitious material) is calculated based solely on the mass of the cementitious material as defined herein, and excludes limestone and the activator admixture itself from the calculation.

[0065] "Natural pozzolan" means a non-calcined natural silified shale mineral that is a Class N Pozzolan is under the chemical and physical requirements of ASTM C-618.

[0066] "Binder" means the cementitious materials and any admixture or activator components for use in the preparation of a concrete composition. In some examples, the binder comprises activator plus at least one of Portland cement and Supplementary cementitious materials (SCMs).

[0067] "Mortar" designates a mixture of cementitious materials, fillers, sands, water and optionally additives or activator.

[0068] "Admixture" means a chemical substance added to a binder, concrete or mortar mix, in minor proportions compared to the primary components, with the purpose ofmodifying and enhancing specific properties of the final material (e.g. concrete or mortar). These properties include, but are not limited to, workability, setting time, strength, durability, and resistance to environmental factors. Admixtures may be chemical and / or mineral in nature and are employed to achieve characteristics in the concrete that cannot be attained by the primary components alone (cement, water, and aggregates). Activators of the invention are admixtures and references to activator is intended to be read as a reference to an activator admixture.

[0069] Concrete admixtures are mixtures that are added to the concrete mixture to enhance its properties and improve its performance. They can be in dry or liquid form. They are typically prepared and sold independently of the concrete and are tailored for different concrete applications. There are many different types of admixtures available, each with its own specific function. Generally, concrete admixtures comprise the following components:

[0070] Plasticisers (also referred to as water reducers or superplasticisers) are admixtures used to reduce the amount of water required to achieve a desired workability in a concrete mixture. Suitable plasticisers include, for example, sulfonated melamine-based polymers, lignosulfonates, sulfonated naphthalene-based polymers, and polycarboxylatebased polymers. For the avoidance of doubt, the term "plasticiser" as used herein refers to dispersing or water- reducing admixtures and does not encompass alkali activators or alkaline chemical activators.

[0071] Retarders: Retarders slow down the setting time of concrete, allowing more time for placement, finishing, and transportation. Commonly used retarders include lignosulfonates, carbohydrates, and citric acid. Retarders and natural pozzolans can also work synergistically in concrete, particularly when it comes to controlling the setting time of the mixture. When used together, retarders and natural pozzolans can help to provide greater control over the setting time of the concrete, particularly in situations where a longer setting time is desirable. For example, in hot weather, the addition of a retarder can help to slow down the rate of hydration and prevent the mixture from setting too quickly. Similarly, in situations where longer transport times are required, the use of a combination of retarders and natural pozzolans can help to ensure that the concrete remains workable and does not set before it can be properly placed.

[0072] Accelerators: Accelerators are admixture components that speed up the setting and hardening of concrete, allowing it to gain strength more quickly. Calcium chloride is a commonly used accelerator, but other types of accelerators, such as triethanolamine or sodium thiocyanate, can also be used.

[0073] Air-Entraining Agents: Air-entraining agents are admixture components that create microscopic bubbles in concrete, which help to improve its durability and workability. They are typically made from natural or synthetic surfactants.

[0074] Corrosion Inhibitors: Corrosion inhibitors are admixture components that are added to concrete to prevent the corrosion of reinforcing steel. They work by forming a protective layer around the steel, which prevents the penetration of corrosive agents.

[0075] The activators described herein are admixtures in that they are incorporated as a minor component of a mixture comprising cementitious materials in order to form a binder, mortar and / or concrete having modified performance characteristics. In certain examples, the activator admixture may be present in a concrete, mortar or binder composition at between 0.25-10% by weight of cementitious material. In certain examples, the activator admixture may be present at between 0.5-8% by weight of cementitious material. In certain examples, the activator admixture may be present at between 1-4% by weight of cementitious material.

[0076] The lower end of the range, including dosages of approximately 0.25-1.5%, may be suitable where the activator is dry-blended directly with Portland cement prior to addition of aggregates and water. In such configurations, intimate particle-to-particle contact between the activator pozzolan fractions and cement grains may enhance dispersion efficiency. Intimate contact may increase surface interaction between reactive phases. Lower total activator quantities may therefore be sufficient to activate supplementary cementitious materials. Lower dosages may also be appropriate where the concrete composition contains relatively high-reactivity supplementary cementitious materials, including finely divided natural pozzolans, silica fume, or metakaolin.

[0077] Intermediate dosages, including for example 0.5-8% by weight of cementitious materials, may be appropriate for blended systems containing moderate-reactivity supplementary cementitious materials such as fly ash, slag, pumicites, volcanic ash, or limestone-containing binders. In certain examples, the activator may enhance dissolution kinetics of reactive phases. In certain examples, the activator may promote formation of carboaluminate phases. In certain examples, the activator may accelerate nucleation of calcium-silicate-hydrate (C-S-H). In certain examples, the activator may improve interfacial bonding within the binder matrix. The dosage within this range may be selected according to the total SCM loading, the specific surface area of the SCM, the particle size distribution of the SCM, and the desired rate of strength development.

[0078] Higher dosages within the range of approximately 5-10% by weight of cementitious materials may be employed in applications requiring enhanced rheological performance in addition to chemical activation. In self-compacting concrete or highly flowable concrete systems, increased activator content may contribute to improved particle packing. Increased activator content may improve dispersion of binder particles. Increased activator content may enhance flowability without segregation. The multi-modal particle size distribution of the activator, particularly where intermediate particles fill interstitial voids between coarser particles, may improve flow characteristics. In certain examples, thispacking effect may reduce bleeding. In certain examples, this packing effect may improve stability of the fresh concrete mixture.

[0079] The appropriate dosage may therefore depend on multiple parameters including: (i) the type and proportion of supplementary cementitious materials; (ii) the reactivity of the SCM; (iii) the particle size distribution of the SCM; (iv) whether the activator is preblended in dry form with cement or introduced during mixing; (v) the desired compressive strength development profile; and (vi) the rheological requirements of the concrete, including whether the composition is intended to function as conventional vibrated concrete or self-compacting concrete.

[0080] The examples described herein demonstrate that the activator is effective within the ranges recited above. The underlying activation mechanism may involve increased surface reactivity. In certain examples, electrostatic interactions may contribute to activation. In certain examples, enhanced nucleation of hydration products may occur. In certain examples, improved interaction between carbonate phases and aluminosilicate phases may occur. These mechanisms support operability across the broader dosage ranges described. A skilled person, having regard to the SCM type, particle size characteristics, and intended application, would be able to determine an appropriate activator dosage within the stated ranges without undue experimentation.

[0081] The activator may comprise some or all of the components described herein and may be prepared in dry powder form. One function of the activator is to increase the chemical reactivity of limestone-containing cementitious systems so that limestone participates in hydration reactions rather than functioning primarily as an inert filler. The activator may enhance dissolution of reactive phases. The activator may promote formation of carboaluminate phases in the presence of limestone. The activator may accelerate nucleation and growth of C-S-H. The activator may improve interfacial bonding within the composite binder matrix. As a result, strength development in limestone-containing concrete compositions may be achieved at a similar or greater rate compared with cementbased concrete compositions without activator, despite partial clinker replacement.

[0082] Accordingly, in one example there is provided a method of increasing limestone reactivity in a cementitious binder matrix comprising limestone and cementitious material, the method comprising adding an activator admixture as described above in relation to the concrete composition or method of producing a limestone concrete composition, to the cementitious material and limestone. In one example the method promotes formation of calcium-silicate-hydrate and / or carboaluminate hydration phases. This method of increasing limestone reactivity as described above is supported by the comparative data set out in Examples 12-17. In Example 12, replacement of 30% cement with limestone resulted in substantial reductions in compressive strength at all ages when compared with the 100% cement control. Incorporation of 3% activator into the same limestone system producedsignificant strength recovery at all early ages (+39% Day 1; +38% Day 3; +30% Day 7 relative to the limestone control), thereby evidencing enhanced binder reactivity. Similarly, in Example 15, the activator-containing 30% limestone system achieved substantially equivalent strength to the 100% cement control by Day 7 despite a 30% reduction in cement content, demonstrating functional activation of the limestone phase within the binder matrix.

[0083] Further evidence of increased limestone reactivity is observed in blended systems comprising limestone and supplementary cementitious materials. In Examples 13, 16 and 17, ternary systems containing 20% limestone and 10% fly ash or natural pozzolan exhibited marked strength deficits relative to the 100% cement control when unactivated. Upon addition of the activator, significant strength recovery and, in certain cases, strength parity or exceedance relative to the full cement control was observed from Day 3 onwards. For example, in Example 16 (20% limestone + 10% fly ash), the activated composition exceeded the 100% cement control at Days 3, 7, 14 and 28 despite 30% cement reduction. These outcomes are consistent with enhanced formation of hydration products within the binder matrix, including calcium-silicate-hydrate and carboaluminate phases, attributable to improved interaction between limestone, cementitious phases and supplementary materials. Collectively, the data demonstrate that addition of the activator increases the effective reactivity of limestone in cementitious systems.

[0084] Concrete comprising activators of the invention plus natural and synthetic (including industrial) pozzolans have a higher rate of strength development and ultimate strength than concrete comprising only natural or synthetic pozzolans. Example 2b and other examples demonstrate this effect. Activators of the invention also have the surprising effect of activating cement and optionally fillers to be more effective binders as shown by the examples.

[0085] Natural pozzolans are siliceous or silico-aluminous materials and are composed of various chemical compounds, including silica, alumina, iron oxide, calcium oxide, magnesium oxide, and potassium oxide. These compounds are responsible for the pozzolanic activity of natural pozzolans and their ability to contribute to the strength and durability of concrete. Where concrete comprises natural pozzolans, their properties play a critical role in the performance of the concrete.

[0086] The reactivity of natural pozzolans is related to their content of reactive silica and alumina, as well as the amorphousness of their structure. These properties determine the pozzolanic activity, which is the ability of the natural pozzolan to react with calcium hydroxide in the presence of water to form calcium silicate hydrate (CSH) and other cementitious compounds that contribute to the strength and durability of the concrete.

[0087] Silicon dioxide (silica) is the primary component of natural pozzolans, accounting for up to 90% of their composition. It is a key component in the formation of the pozzolanicreaction, and it contributes to the development of the strength and durability of the resulting concrete. The amount of reactive silica in the natural pozzolan is an important factor in its pozzolanic activity. Aluminium oxide (alumina) is another important component of natural pozzolans, and it plays a key role in the formation of the pozzolanic reaction. Alumina reacts with calcium hydroxide to form calcium aluminate hydrates, which contribute to the strength and durability of the concrete.

[0088] The percentage of each of the chemical compounds found in natural pozzolans can vary depending on the type of natural pozzolan and its geological origin. Controlling the chemical composition of natural pozzolans before using them in concrete mixtures is important to ensure that they result in the desired concrete properties once mixed. They must also be compatible with the other ingredients in the mix and not create compounds detrimental to concrete structure.

[0089] Activator admixtures potentiate limestone and other fillers in concrete compositions. The present invention provides a method for enhancing the performance of concrete compositions in which a portion of the cementitious material is replaced with limestone. It has been found that the use of activator admixtures as described herein significantly improves the strength of such limestone-containing concrete, compensating for the reduced cement content and maintaining or even enhancing the performance of the final composition.

[0090] The activator admixture comprises a pozzolan component that includes at least a first pozzolan portion and a second pozzolan portion, each having distinct median particle sizes and / or chemical compositions. This combination is believed to enhance the interaction between limestone and the cementitious matrix, facilitating improved hydration and secondary cementitious reactions. The activator admixture may also comprise an electrostatic charge, which is believed to promote better interfacial bonding and mixing between the limestone particles and cementitious phases.

[0091] Without wishing to be bound by theory, it is believed that the addition of the activator admixture of the invention increases the dissolution rate of calcium carbonate in limestone, promoting its participation in cementitious reactions. This in turn enhances the formation of calcium-silicate-hydrate (C-S-H) phases, contributing to improved early and long-term strength. The higher early strength observed is indicative of a reduction in the setting time in limestone-containing concrete, ensuring appropriate hydration kinetics even with high limestone replacement levels.

[0092] In some examples, the activator admixture comprises reactive pozzolans that promote pozzolanic activity in the presence of limestone, forming additional hydration products that improve the mechanical integrity of the hardened material. The particle size distribution of the activator admixture is optimised to provide enhanced packing density, thereby reducing voids and improving the densification of the concrete matrix. In particular,the activator admixture may exhibit a first volume density peak between 0.3 and 1.5% for particles at 0.5-1.5 pm and a second volume density peak greater than 3% for particles between 10-80 pm, with a volume density ratio of 1:3 to 1:6.

[0093] The activator admixture may also include a plasticiser component, which may be selected from polycarboxylates, naphthalene-based plasticisers, lignosulphonates, and dry powder plasticisers. The inclusion of a plasticiser may also improve workability, particularly in highly reinforced sections, complex formwork applications, or low water-cement ratio systems where improved flow characteristics are required.

[0094] In some embodiments, the activator admixture enables the replacement of up to 30% of the cementitious material with limestone without reducing compressive strength, thereby providing a more sustainable and cost-effective alternative to conventional cement formulations. In other examples the limestone replacement is less than 15%, less than 20% or less than 25% and each replacement level achieves enhanced strength compared to cement alone or replacement SCM (see example 11). This formulation has been shown to maintain a compressive strength of at least 25 MPa at 28 days, even with high limestone substitution levels.

[0095] The activator admixture may be pre-mixed with limestone before being incorporated into the concrete mixture, ensuring uniform dispersion and reactivity.Additionally, the activator admixture may be subjected to a controlled electrostatic charge, improving compatibility between limestone, cement, and hydration products.

[0096] The present invention thus provides an improved concrete composition and production method, which allows for a higher proportion of limestone replacement while maintaining or enhancing strength, durability, and workability. This advancement enables a significant reduction in cement content, supporting carbon footprint reduction goals in the construction industry while ensuring the structural integrity of the final concrete product.

[0097] Portland limestone cement (PLC) is produced through a multi-step manufacturing process that integrates limestone directly into the cement production pathway. The process begins with the extraction of raw materials, primarily limestone (CaCOs) and clay or shale, which are quarried and transported to the cement works. These materials are then crushed, ground into fine particles, and mixed in precise proportions before being heated in a kiln at approximately l,450°C (2,640°F) to form clinker nodules. After cooling, the clinker is ground into a fine powder and blended with gypsum, which acts as a set retarder, along with a higher proportion of finely ground limestone compared to traditional Portland cement. The final mixture undergoes extensive milling in large tube mills for about 30 minutes to produce the final PLC product.

[0098] The key distinction between PLC and traditional Portland cement is the increased limestone content in the final cement blend. This reduction in clinker proportion leads to lower CO2 emissions, as the energy-intensive kiln stage, responsible for most of cement'scarbon footprint, is responsible for the majority of CO2 released in cement production. The interground limestone in PLC is finely mixed with clinker particles during the final milling stage.

[0099] In contrast to the PLC manufacturing process, which incorporates limestone directly into cement production, the present invention takes a fundamentally different approach to introducing limestone into concrete formulations. Rather than intergrinding limestone with clinker, the invention involves blending an activator admixture with limestone powder before or during its incorporation into the concrete mix. This blended mixture is added to cementitious materials, including supplementary cementitious materials (SCMs), water, sand, and, optionally, aggregate. The addition of the activator admixture unexpectedly enhances the reactivity of limestone rather than it simply being present as a passive filler within the cement. Thus improving its role in hydration reactions and secondary cementitious activity. Accordingly, in one example the method of preparing a concrete composition does not include the intergrinding of limestone with cement.

[0100] Unlike PLC, where limestone is integrated into the cement during production, this approach allows for a more active and controlled use of limestone in concrete. The activator admixture is believed to enhance the dissolution of calcium carbonate, promoting its interaction with cement hydration products and leading to the formation of additional calcium-silicate-hydrate (C-S-H) phases. This compensates for the reduction in cement content while also improving the microstructural density and durability of the concrete.

[0101] Another advantage of this method is its flexibility, as the limestone content can be adjusted independently of cement manufacture. This contrasts with PLC, where the limestone proportion is determined at the grinding stage and remains fixed throughout cement distribution and use. By instead blending limestone with an activator at the mixing stage, concrete formulations can be tailored to specific performance requirements, allowing for higher limestone replacement levels without compromising strength or durability.Additionally, the activator admixture can modify the rheology of the concrete, improving workability in applications such as highly reinforced sections, complex formwork, or low water-cement ratio mixes.

[0102] In summary, while PLC is a modified cement formulation that passively incorporates limestone through intergrinding, the present invention introduces a more dynamic and reactive approach by blending limestone with an activator admixture before or during the preparation of the concrete mix. This is believed to enhance hydration kinetics and microstructural development as well as providing greater control over limestone's performance in concrete, ultimately enabling a more sustainable, adaptable, and high-performance cementitious system.

[0103] Limestone-containing concrete prepared with an activator admixture offers enhanced performance, sustainability, and cost efficiency across a range of structural andinfrastructure applications. In bridges, overpasses, and tunnels, the improved durability and reduced shrinkage contribute to long-term structural integrity. The optimised workability and setting characteristics make it particularly suitable for precast elements, such as beams, panels, and culverts, while the lower heat of hydration makes it ideal for mass concrete applications, including dams and foundations, where thermal cracking is a concern.

[0104] In urban infrastructure, the reduced clinker content supports low-carbon construction, making it well-suited for roads, pavements, and large-scale housing projects. The enhanced sulfate resistance and reduced permeability also improve performance in water infrastructure, such as treatment plants, reservoirs, and canals, where long-term durability is critical. Additionally, the improved particle packing and flowability enable its use in high-performance concrete applications, including ultra-high-performance concrete and self-compacting concrete, which require dense, highly reinforced sections with optimised workability.

[0105] By enhancing hydration kinetics, microstructural development, and rheology, activator-enhanced limestone concrete enables higher limestone replacement levels without compromising strength or durability, providing a cost-effective and environmentally sustainable alternative to traditional cement-based formulations. Experimental data provided in Examples 11-17 demonstrate that the activator admixtures of the invention materially increase the reactivity of limestone-containing cement systems, and blended limestone-pozzolan systems, beyond what would be expected from simple filler effects or conventional water reduction.

[0106] Example 11 illustrates the effect of the activator in a 30% cement reduction system comprising natural pozzolans (Pozzl - pumicite) and limestone. Two blended systems were tested: 15% Pozzl + 15% limestone and 10% Pozzl + 20% limestone, each incorporating approximately 3.1% activator relative to binder. Both activated blends exceeded the strength of the 100% cement control at all measured ages despite a 30% reduction in cement content. At Day 1, strengths increased from 9 MPa (control) to 14 MPa and 12 MPa respectively. At Day 28, strengths reached 66 MPa and 58 MPa compared with 46 MPa for the control. At Day 56, the 15% Pozzl + 15% limestone mix achieved 75 MPa, representing an increase of 22 MPa over the control. These results confirm that the activator not only compensates for cement reduction but enables strength enhancement beyond conventional cement formulations.

[0107] Example 12 demonstrates performance in a binary 30% limestone replacement system. When 30% cement was replaced with limestone, compressive strength was significantly reduced relative to the 100% cement control. However, when the same limestone replacement was combined with 3% activator, compressive strength increased relative to the limestone control at all ages. Strength improvements relative to the limestone + water reducer mix were approximately +39% at Day 1, +38% at Day 3, +30%at Day 7, and +8% at Day 28. This indicates enhanced binder reactivity and hydration kinetics induced by the activator.

[0108] Example 13 further demonstrates this effect in a ternary blended system comprising 20% limestone and 10% fly ash. Replacement of 30% cement with limestone and fly ash resulted in reduced strength relative to the 100% cement control. However, addition of 3% activator increased compressive strength relative to the limestone-fly ash + water reducer control at all ages. Strength improvements were approximately +47% at Day 1, +33% at Day 3, +20% at Day 7, and +15% at Day 28. The treated mix exhibited comparable or improved workability relative to controls, again confirming that performance gains arise from activation of binder chemistry. Taken together, Examples 11-13 demonstrate three important and technically distinct effects:• In blended pozzolan-limestone systems, the activator enables strength exceeding that of 100% cement despite 30% cement reduction.• In binary limestone systems, the activator materially recovers early-age strength lost due to cement substitution.• In ternary limestone-pozzolan (e.g. fly ash) systems, the activator enhances early pozzolanic reactivity and accelerates strength development across multiple supplementary cementitious materials. In this example, the pozzolan may be selected from natural, industrial or synthetic pozzolans e.g. pumice, fly ash, slag, silica fume, metakaolin (thermally activated kaolin clay), and rice husk ash.

[0109] Examples 14-16 further demonstrate that the activator provides substantial performance enhancement in concrete formulations where workability is adjusted to comparable levels across mixes. In these examples, the activator-containing compositions achieved higher compressive strength. This confirms that the activator functions as a reactive component that improves hardened-state performance.

[0110] Example 14 establishes the intrinsic effect of the activator in a 100% cement system. At substantially identical initial slump, the activator-containing mix exhibited substantial strength increases at all measured ages relative to the 100% cement control. This suggests that the activator enhances cement hydration and strength development even in the absence of limestone or supplementary cementitious materials, supporting the conclusion that its action extends beyond simple filler activation. Examples 15 and 16 show that these benefits translate directly into reduced-cement limestone-containing systems. In Example 15 (30% limestone replacement), incorporation of 3% activator significantly increased compressive strength relative to the limestone-only control at all ages and enabled substantial strength recovery relative to the 100% cement control, reaching nearequivalent performance at intermediate ages despite significant cement reduction. In Example 16 (20% limestone + 10% fly ash), the activator-containing ternary blend matched the 100% cement control at early age and exceeded it at later ages, while alsoproviding large strength increases relative to the corresponding non-activated limestone-fly ash control. These results demonstrate that the activator materially increases the effective binding contribution of limestone and supplementary cementitious materials, mitigating or reversing the strength penalties typically associated with cement substitution.

[0111] Example 17 further supports the general applicability of the invention by demonstrating strength recovery in an alternative limestone-pozzolan blend (20% limestone + 10% Pl). Although the activator-containing limestone-Pl system did not consistently exceed the 100% cement control at all later ages, it delivered substantial strength enhancement relative to the corresponding non-activated blend and achieved substantially equivalent performance at intermediate age. This confirms that the activator increases the reactivity of multiple limestone-SCM systems, with the magnitude of enhancement dependent on the chemistry and intrinsic reactivity of the supplementary material.

[0112] Taken together, Examples 11-17 demonstrate that the activator converts limestone from functioning primarily as a passive filler into a chemically interactive component of the binder system, enabling significant cement reduction while maintaining or improving strength development across a range of blended cement formulations.

[0113] Without wishing to be bound by theory, it is believed that the activator promotes increased dissolution of calcium carbonate, enhanced formation of carboaluminate phases, accelerated nucleation of C-S-H, and improved interfacial bonding within the composite binder matrix. In ternary systems, the activator may also accelerate fly ash reaction kinetics, thereby improving synergistic interaction between carbonate and aluminosilicate phases. These results confirm that the activator converts limestone from functioning primarily as a passive filler into a chemically interactive and performance-enhancing component within the cementitious matrix. This enables higher limestone and SCM replacement levels while maintaining or improving strength development, thereby supporting reduced cement content and lower embodied carbon without compromising structural performance.

[0114] In one example, the invention provides an activator comprising an activated pozzolan. In one example, the pozzolan is selected from a natural pozzolan and a synthetic pozzolan. In one example, the invention provides a natural pozzolan wherein the pozzolan has undergone a process which activates it. In one example, the activation process comprises at least one of application of an electrostatic charge, grinding the pozzolan to a desired particle size and controlling the particle size distribution. Similarly, synthetic pozzolans will have undergone processes that provide high levels of surface activation. This can occur during their production which is typically through thermal activation during production of fly ash or slag or other high temperature processes.

[0115] Preferably the activated pozzolans comprised in an activator have a moisture content of less than about 5%. Even though the activators of the present invention can be produced and used with a moisture content of greater than 5%, enhanced stability, mixing and formulation is achieved at lower moisture contents. Therefore, in a further example, the activator comprises a moisture content of less than about 3%. The moisture content may be adjusted to be within this range, or maintained within this range if material obtained is already at the desired moisture content.

[0116] The inventors have found that activators combined with limestone and / or natural or synthetic pozzolans function as a reactive component of the binder and may provide improved workability, strength and durability in limestone-containing concrete compositions. These properties enable replacement of a portion of Portland cement that would otherwise be required in a conventional concrete mixture.

[0117] In certain examples, a concrete composition comprising limestone and / or supplementary cementitious materials, wherein the activator is present at between 0.25-10% by weight of cementitious material, optionally between 0.5-8%, and in certain implementations between 1-4% by weight of cementitious material, may yield concrete exhibiting substantially the same or improved workability, compressive strength and durability compared with corresponding compositions containing limestone or SCMs but without activator. The cementitious material refers to the total binder fraction active during hydration of the concrete composition. In certain examples, the cementitious material comprises Portland cement, optionally in combination with limestone and / or supplementary cementitious materials.

[0118] By way of illustrative example, a concrete formulation may comprise approximately 111 kg less Portland cement than a reference composition, with that reduction offset through incorporation of an activator in an amount of approximately 7.2 kg together with increased aggregate and / or filler content. In such an example, comparable strength and durability performance may be achieved while reducing clinker content. This example is illustrative of the cement-reduction capability achievable within the dosage ranges described herein and is not intended to limit the scope of operable activator quantities. A person skilled in the art, having regard to the proportion of limestone present and the required performance characteristics, would be able to select an appropriate activator dosage within the stated ranges to achieve comparable results.

[0119] Pozzolans can be described in terms of their chemical composition. The pozzolans are present in activators in a range and in proportions which assist in achieving the chemical composition described below. These activators provide the user with a concrete product with enhanced durability, strength and setting time. The inventors have shown that activators of the invention can be prepared from materials in a wide range of chemical compositions. In some examples, the activator chemical composition comprises SiOz at arange from 20-80% by volume of the activator. In some examples, the activator chemical composition comprises AI2O3 in a range of 5-40% by volume of the activator. In an alternative embodiment, the invention comprises the following chemical composition range:;0120] In one particular example, the chemical composition comprises SiO2 at a range from 30-40%, and AI2O3 in a range from 7-10% by volume of the activator. The above percentages can be achieved using multiple pozzolan minerals, combined in proportions that are able to be ascertained by those of skill in the art and as described herein.

[0121] In one example, an activator of the invention comprises a first pozzolan portion and a second pozzolan portion, wherein the first and second pozzolan portions have different chemical compositions and different median particle sizes. The differences referred to herein relate to the respective properties of the first pozzolan portion and the second pozzolan portion considered individually, and not to the Dv50 or chemical composition of the blended activator as a whole.

[0122] As referred to herein, a different chemical composition refers to a difference of at least 5% w / w in the amount of silicon dioxide (SiCb) or aluminium oxide (AI2O3) between the first and second pozzolan portions. In certain examples, the difference in silicon dioxide content between the first and second pozzolan portions is at least 5%, at least 10%, or at least 15% w / w. In certain examples, the difference in aluminium oxide content between the first and second pozzolan portions is at least 5%, at least 10%, or at least 15% w / w. The difference may relate to one or both of silicon dioxide and aluminium oxide.

[0123] A compositional difference of at least 5% w / w in silicon dioxide or aluminium oxide between the first and second pozzolan portions is sufficient to create a measurable difference in surface chemistry, dissolution kinetics and reactive phase availability during hydration. Even a 5% variation in oxide composition between two mineral fractions can alter the relative availability of silicate and aluminate species in the pore solution, thereby modifying the rate and pathway of secondary hydration reactions. In certain examples, a difference of at least 10% w / w in silicon dioxide or aluminium oxide provides a more pronounced differentiation in reactivity between the first and second pozzolan portions. At this level of compositional divergence, the two portions contribute distinctly to hydration reactions, with one portion preferentially enhancing silicate-driven C-S-H formation and the other contributing to aluminate-driven carboaluminate or related phase development. This compositional distinction supports synergistic interaction within the binder matrix. In certain examples, a difference of at least 15% w / w in silicon dioxide or aluminium oxide results in clearly differentiated mineralogical behaviour between the first and second pozzolanportions. At this level of divergence, the portions exhibit materially different pozzolanic reactivity profiles and dissolution rates, which enhances the ability to tailor early-age strength development, long-term strength gain, and microstructural densification through controlled multi-component interaction. The compositional difference may relate to silicon dioxide, aluminium oxide, or both. A difference in silicon dioxide content influences silicate-driven hydration and C-S-H nucleation kinetics. A difference in aluminium oxide content influences aluminate reactivity and the formation of carboaluminate and related hydration products. In certain examples, differences in both oxides are present, providing complementary and synergistic effects within the cementitious system. The inventors have found that such defined compositional differentiation between discrete pozzolan portions contributes to enhanced activation behaviour compared to a system comprising chemically homogeneous pozzolan particles of similar size distribution.

[0124] As referred to herein, a different median particle size refers to a difference in the Dv50 median particle size of the first pozzolan portion relative to the Dv50 median particle size of the second pozzolan portion. In certain examples, the Dv50 of the first pozzolan portion differs from the Dv50 of the second pozzolan portion by at least 5% relative to the smaller Dv50 value. In certain examples, the difference in Dv50 is at least 10%, at least 20%, or at least 50%. In certain examples, the absolute difference in Dv50 between the first and second pozzolan portions is at least 0.5 pm, at least 1 pm, at least 5 pm, or at least 10 pm.

[0125] In examples where the activator comprises an intermediate particle size fraction and a coarse particle size fraction, the intermediate particle size peak may range from 0.5-1.5 pm and the coarse particle size peak may range from 10-80 pm. The inventors have found that this structured separation of particle size domains facilitates optimal interstitial filling, whereby particles of the intermediate fraction occupy void spaces between particles of the coarse fraction. This enhances packing density within the binder matrix and contributes to microstructural densification during hydration.

[0126] As referred to herein, a "different median particle size" relates to the Dv50 median particle size of the first pozzolan portion relative to the Dv50 median particle size of the second pozzolan portion, each measured independently prior to blending into the activator. In certain examples, the Dv50 of the larger portion is at least 2x the Dv50 of the smaller portion (i.e., at least a 100% relative difference). Such a difference represents a minimum threshold at which the two portions occupy measurably distinct particle size regimes and exhibit divergent packing and surface area behaviour.

[0127] In certain examples, the Dv50 of the larger portion is at least 4x, at least 6x, or at least lOx the Dv50 of the smaller portion. These progressively larger separations correspond to increasing structural differentiation between the particle fractions. At differences of 4x and above, the portions contribute distinctly to packing hierarchy. Atdifferences of 6x and above, the intermediate fraction functions primarily as an interstitial filler relative to the coarse fraction. At differences of lOx and above, the particle populations occupy clearly separated size domains consistent with the formation of discrete peaks in a bi-modal or multi-modal particle size distribution.

[0128] Accordingly, in some examples there is provided a limestone concrete composition, a method of producing a limestone concrete composition, or a use of a limestone concrete composition wherein the Dv50 of the second pozzolan portion is at least 2 times the Dv50 of the first pozzolan portion. In other examples, the Dv50 of the second pozzolan portion is at least 4 times the Dv50 of the first pozzolan portion. In other examples, the Dv50 of the second pozzolan portion is at least 6 times the Dv50 of the first pozzolan portion. In other examples, the Dv50 of the second pozzolan portion is at least 10 times the Dv50 of the first pozzolan portion.

[0129] In certain examples, the absolute difference in Dv50 between the first and second pozzolan portions is at least 10 pm, optionally at least 20 pm, at least 30 pm, or at least 50 pm. Differences within these ranges correspond to particle populations residing in different size bands rather than reflecting minor statistical variation within a single distribution.Absolute separations of 20-50 pm are consistent with the intermediate (sub-2 pm) and coarse (10-80 pm) peak regions described herein.

[0130] In certain examples, the first and second pozzolan portions occupy distinct particle size regions and form separate peaks within a bi-modal or multi-modal particle size distribution of the activator. In such examples, the first pozzolan portion comprises an intermediate particle size fraction and the second pozzolan portion comprises a coarse particle size fraction. The presence of discrete peaks confirms that the portions are intentionally differentiated particle populations rather than merely a broadened unimodal distribution.

[0131] In one example, there is provided a method of producing a limestone concrete composition comprising:a) obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b) combining the first and second pozzolan portions to form a pozzolan component; and c) combining cementitious material, limestone, water, and an activator admixture comprising the pozzolan component and a plasticiser to form the limestone concrete composition,wherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0132] In one example, there is provided a method of producing a limestone-containing concrete composition comprising the steps of:a) obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b) combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c) providing a plasticiser;d) optionally forming an activator admixture comprising the pozzolan component and the plasticiser;e) combining the pozzolan component, plasticiser (where present), cementitious material, limestone and water to form the limestone concrete composition, wherein the pozzolan component may be combined with the limestone, the cementitious material, or both, prior to addition of water,wherein the pozzolan component may be added before, during, or after addition of water,wherein the plasticiser may be added prior to, concurrently with, or subsequent to addition of the pozzolan component, andwherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0133] In embodiments of the method described above, the order in which the cementitious material, limestone, pozzolan component and plasticiser are combined is not limited to any particular sequence unless otherwise specified. The activator admixture may be pre-formed by combining the pozzolan component and plasticiser prior to introduction into the cementitious mixture, or the pozzolan component and plasticiser may be introduced separately and allowed to associate in situ during mixing, for example with cementitious material, limestone or supplementary cementitious materials (SCMs). The pozzolan component may be combined with the limestone prior to addition of the cementitious material, may be combined with the cementitious material prior to addition of the limestone, or may be blended with both simultaneously as part of a dry mix. Water may be added after dry blending of some or all components, or may be introduced concurrently with one or more of the solid components during mixing. Accordingly, the method encompasses batch, staged, simultaneous, dry-blend, and wet-mix processes commonly employed in concrete production.

[0134] In certain embodiments, however, the activator admixture is prepared as a discrete composition prior to contact with the cementitious material. In such embodiments,the pozzolan component and plasticiser are combined in advance of addition to the concrete mixture, thereby forming a pre-formed activator admixture that is subsequently introduced into a mixture comprising cementitious material and limestone.

[0135] Pre-formation of the activator admixture may provide practical advantages in manufacture, storage and transport. The activator admixture may be produced at a first location, stored as a dry or substantially dry composition, and transported separately from the cementitious material and limestone prior to batching. Separation of the activator admixture from the cementitious material prior to hydration may permit controlled dosing, improved handling characteristics, and enhanced consistency between batches.

[0136] Pre-combination of the pozzolan component and plasticiser may also allow more effective association between these components prior to hydration. Without wishing to be bound by theory, intimate pre-mixing may promote uniform mixing of pozzolan particles and the plasticiser, reduce agglomeration of fine particle fractions, and improve dispersion behaviour when introduced into the cementitious matrix.

[0137] In certain examples, the pre-formed activator admixture is first combined with limestone prior to addition of cementitious material. Pre-treatment or dry blending of limestone with the activator admixture may increase surface interaction between limestone particles and reactive pozzolanic species prior to hydration, thereby promoting enhanced reactivity within the binder system.

[0138] In alternative embodiments, the pre-formed activator admixture is first combined with cementitious material prior to addition of limestone. In further embodiments, the activator admixture is combined with one or more supplementary cementitious materials (SCMs) prior to addition to the concrete mix. Such sequential addition may promote improved distribution of reactive particles within the binder phase before full hydration commences.

[0139] In other embodiments, the pozzolan component and plasticiser are not preblended as a discrete activator admixture but instead are combined in situ during mixing of the cementitious material, limestone and water. In such embodiments, formation of the activator occurs within the wet mix and functional interaction between the pozzolan component, limestone and cementitious phases develops during mixing and hydration.

[0140] The inventors have found that staged or sequential addition of the pozzolan component and plasticiser prior to or during hydration can improve dispersion, reduce agglomeration of fine particle fractions, enhance interaction with limestone particles, and promote formation of hydration products including calcium-silicate-hydrate and carboaluminate phases. Sequential preparation prior to hydration may further distinguish the present methods from conventional admixture systems in which dispersants are introduced directly into a wet concrete mix without prior structured association with reactive pozzolanic components.

[0141] The order of addition may therefore be selected according to batching method, plant configuration, limestone replacement level, transport conditions, storage logistics, or desired rheological and strength performance, without departing from the scope of the invention.

[0142] In certain examples, the pozzolan component comprises 20-80% w / w silicon dioxide (SiCb) and 5-40% w / w aluminium oxide (AI2O3). This compositional range encompasses natural and synthetic pozzolans capable of participating in secondary hydration reactions within a cementitious system. Silicon dioxide within this range provides reactive silicate species for formation of calcium silicate hydrate (C-S-H) phases, while aluminium oxide contributes to aluminate reactivity and the formation of carboaluminate and related hydration products. The lower bounds ensure sufficient reactive oxide content to meaningfully contribute to hydration chemistry, while the upper bounds accommodate mineralogical variability across different pozzolan sources without compromising binder integrity.

[0143] In certain examples, the pozzolan component comprises 20-80% w / w silicon dioxide (SiCb) and 5-40% w / w aluminium oxide (AI2O3). This compositional range encompasses natural and synthetic pozzolans capable of participating in secondary hydration reactions within a cementitious system. Silicon dioxide within this range provides reactive silicate species for formation of calcium silicate hydrate (C-S-H) phases, while aluminium oxide contributes to aluminate reactivity and the formation of carboaluminate and related hydration products. The lower bounds ensure sufficient reactive oxide content to meaningfully contribute to hydration chemistry, while the upper bounds accommodate mineralogical variability across different pozzolan sources without compromising binder integrity.

[0144] In certain examples, the pozzolan component comprises 40-80% w / w silicon dioxide and 10-40% w / w aluminium oxide. Compositions within this range exhibit increased availability of reactive silicate and aluminate phases, promoting enhanced pozzolanic reactivity and improved contribution to binder microstructure. Higher silicon dioxide content within this range supports sustained C-S-H development, while aluminium oxide levels of 10% or greater promote formation of stabilising aluminate-containing hydration phases. This compositional window may provide improved synergy when the activator comprises differentiated pozzolan portions.

[0145] In certain examples, the pozzolan component comprises 30-40% w / w silicon dioxide and 7-15% w / w aluminium oxide. This narrower compositional range may correspond to particular mineral classes or engineered pozzolan blends in which balanced silicate and aluminate reactivity is desired. Within this range, the relative proportions of silicon dioxide and aluminium oxide may be tailored to optimise early-age strength development, chloride binding capacity, and long-term microstructural densification. Suchcompositions may be particularly suitable where controlled differentiation between first and second pozzolan portions is employed.

[0146] In embodiments where the first and second pozzolan portions comprise different chemical compositions within the ranges described above, the differentiation in oxide content contributes to distinct dissolution kinetics and reactive phase availability. A higher silicon dioxide portion may preferentially enhance silicate-driven C-S-H formation, while a comparatively higher aluminium oxide portion may contribute to aluminate-driven phase development. The defined compositional ranges therefore provide a framework within which controlled chemical differentiation can be achieved while maintaining overall compatibility with cementitious hydration processes.

[0147] In one example, the invention provides a method of producing an activator composition comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a second pozzolan portion with a second chemical composition;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. mixing the pozzolan component with a plasticiser to produce an activator composition,wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide, and 5-40% aluminium oxide, wherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

[0148] In one example, the pozzolan component comprises 40-80% w / w silicon dioxide and 10-40% w / w aluminium oxide.

[0149] In one example, the pozzolan component comprises 30-40% w / w silicon dioxide and 7-15% w / w aluminium oxide.

[0150] In one example, the invention provides a method of producing an activator for use as an admixture for concrete comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a first particle size Dv50,b. obtaining a second pozzolan portion with a second chemical composition and a second particle size Dv50;c. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;d. mixing the pozzolan component with a plasticiser to produce an activator compositionwherein the first and second pozzolan portions comprise different Dv50 median particle sizes and / or different chemical compositions.

[0151] The plasticiser may be a powdered plasticiser. In one example, the mixing period is at least five minutes. This ensures that the different materials blend and facilitates the interstitial filling referred to herein which assists in providing a concrete / mortar product with the enhanced properties described herein. The plasticiser may be present at varying concentrations depending on the application of the concrete and the water demand and placement properties. In some example the plasticiser is present at 8-40%, 10-40%, or 10 to 25% w / w of activator. Without wishing to be bound by theory, it is believed that the plasticiser interacts with the pozzolan components to facilitate a stable powdered mixture with properties that enable enhanced reactivity. This enhanced reactivity leads to the unexpected early strength observed in trials outlined in the examples. This unexpected activity of the activator components and optionally additional supplementary cementitious materials added to the mix is believed to be at least partially achieved by the electrostatic activation of activator particles resulting in their reduced clumping, and enhanced interstitial filling as described herein.

[0152] In one example, the method of producing an activator for use as an admixture for concrete comprises a step of applying an electrical charge to one or more activator components. The activator components may comprise any one of the activator, the pozzolan component, the first, second or a further pozzolan portion, or the plasticiser.

[0153] The activator admixtures of the present invention may include pozzolans and a plasticiser in powdered form. During the mixing process, these components may be subjected to electrostatic forces, which may be generated by a variety of mechanisms. In one example, as the mixture undergoes mechanical agitation, friction between the particles causes them to acquire an electrostatic charge. This phenomenon increases the surface energy of the particles, making them more reactive. Alternatively, an external electrical charge can be applied to the admixture to achieve the same effect, enhancing the activation process further. It is important to distinguish this process of mixing from the process of intergrinding which reduces particle size and can also impart increased reactivity to interground particles.

[0154] When the components are mixed, the generated electrostatic forces are believed to result in the particles repelling each other. This repulsion prevents the particles from clumping together, ensuring a uniform dispersion of the pozzolans and plasticiser throughout the concrete / mortar mix. This uniform dispersion assists in achieving a consistent and homogeneous concrete microstructure. An improved microstructure also minimises the occurrence of weak points within the concrete. This results in a more consistent material with improved mechanical properties. Additionally, the uniform dispersion contributes to a reduction of pore size and connectivity within the concrete, which enhances its overall durability and resistance to environmental factors as exemplified in example 4.

[0155] Electrostatic activation is believed to significantly increase the chemical reactivity of the pozzolans within the concrete mix. Pozzolans such as those described herein typically react with calcium hydroxide, a by-product of the cement hydration process. This reaction results in the formation of additional cementitious compounds, notably calcium silicate hydrate (CSH) from SiO2 and CAH from AI2O3 which make up the primary binding phase in concrete and are essential for the concrete's strength and durability. This increased formation of CSH and CAH directly correlate with higher compressive and tensile strength in the concrete. By increasing the surface energy of the pozzolans through electrostatic activation, their reactivity is enhanced thus leading to a more efficient and accelerated pozzolanic reaction, producing more CSH and CAH. The presence of additional CSH and CAH improves the overall strength and durability of the concrete, contributing to its long-term performance.

[0156] The improved dispersion of pozzolans and plasticiser within the concrete mix, believed to result from electrostatic activation, plays a significant role in reducing the concrete's permeability. The formation of additional CSH and CAH helps to fill the pores within the concrete, decreasing the pore size and connectivity. This reduction in porosity leads to decreased permeability, enhancing the concrete's resistance to water and chemical ingress. Consequently, the concrete becomes more durable and better suited for use in harsh environments. Example 4 describes experiments carried out which exemplify the increased durability and performance of activator containing concrete with respect to water resistance, chloride penetration, and reduction in voids.

[0157] Concrete that incorporates the electrostatically activated admixture demonstrates enhanced durability. The increased strength and reduced permeability contribute to the concrete's ability to withstand environmental degradation. This includes improved resistance to freeze-thaw cycles, sulphate attack, and alkali-silica reaction. The enhanced durability makes this concrete suitable for use in a wide range of demanding construction applications, where long-term performance is critical.

[0158] In one example, an external electrostatic field is applied to the dry powder form of the activator. The mixture of pozzolans and plasticiser is placed in a chamber equipped with electrodes that generate an electrostatic field with voltages ranging from 20 to 50 kV. The electrodes can deliver a power output of 2 to 10 kW, ensuring a strong and consistent electrostatic field. The flow rate of the powder through the chamber is maintained at a rate which achieves a power delivery of at least 0.1 to 0.6 kWh / kg of activator powder. This power delivery ensures uniform exposure to the electrostatic field and a uniform charge distribution across the particles.

[0159] In a further example, the dry powder activator is charged using an electrostatic spraying technique. The pozzolans and plasticiser mixture is fed through an electrostatic spray gun, which imparts a charge to the particles as they are sprayed onto a collectionsurface. The spray gun operates at voltages of 30 to 60 kV, with a power output of 1 to 3 kW. The flow rate of the powder through the spray gun is controlled at a rate to achieve at least 0.1 to 0.6 kWh / kg of activator powder. The charged particles are collected and subsequently prepared for use in a concrete or mortar mixture.

[0160] In another example, the activator comprising pozzolans and a plasticiser is subjected to triboelectric charging in a fluidized bed. The dry powder is fluidised using a stream of air, optionally at a flow rate of 50 to 200 m3 / hr. As the particles collide with each other and the walls of the fluidised bed chamber, which are typically lined with a triboelectric material, they become triboelectrically charged. Preferably the voltage generated during this process is between 5 to 25 kV. In one example, the activator is subjected to an electrical charge of between about 0.1 to 0.6 kWh / kg of activator powder. This method utilises the principles of triboelectric charging to generate electrostatic forces, enhancing the properties of the activator for use in concrete.

[0161] In one example, the electrostatic charge applied to the activator components is generated through the mechanical mixing process itself. The dry powder form of the activator, comprising pozzolans and a plasticiser, is subjected to mixing in a mixer. The mixer operates at a speed of 1500 to 3000 rpm, generating friction between the particles. This friction induces electrostatic charges. The power output of the mixer can be adjusted between 1 to 5 kW to control the intensity of the mixing process. This method leverages the inherent frictional forces in mixers to induce the electrostatic effect, enhancing the reactivity and dispersion of the activator components. It will be appreciated by those of skill in the art that mixing and application of an electrostatic charge using this method does not require the size reduction of particles that may be achieved through intergrinding. Intergrinding negatively affects particle size distribution within a mixture, causing larger particles to experience a proportionally greater size reduction compared to smaller particles. This leads to an homogenisation of particle sizes which compromises the benefits of using multiple particle sizes achieved through interstitial filling as referred to herein.

[0162] In a further example, an electrostatic charge is applied to the activator using a corona discharge. The mixture of pozzolans and plasticiser is passed through a region where a high-voltage electrode generates a corona discharge. The electrode operates at voltages ranging from 40 to 80 kV, with a power output of 2 to 6 kW. The flow rate of the powder through the corona discharge region is maintained at a rate sufficient to achieve an electrical charge of between about 0.1 to 0.6 kWh / kg of activator powder. The ions produced by the corona discharge attach to the activator particles, imparting an electrostatic charge in a controlled and efficient way.

[0163] In a further example, the activator components are subjected to electrostatic fluidisation. The pozzolans and plasticiser mixture is placed in an electrostatic fluidised bed where a combination of fluidisation and electrostatic charging occurs. In one example thefluidising air is ionised at a voltage of 15 to 35 kV. The fluidised and ionised air passes through the powder, charging the particles. The power output for ionizing the air is typically between 0.1 to 0.6 kWh / kg of activator powder. This dual action of fluidisation and charging achieves both dispersion and reactivity of the activator components.

[0164] In one example, the pozzolan component comprises a chemical composition comprising 40-80% w / w silicon dioxide, and 10-40% aluminium oxide. In a further example, the pozzolan component comprises a chemical composition of 20-80% w / w silicon dioxide, and 5-40% aluminium oxide.

[0165] In a further example, the invention provides a method of preparing an activator composition comprising the steps of:a. obtaining a first natural pozzolan portion with a first Dv50 particle size;b. combining the first natural pozzolan portion with a second natural pozzolan portion with a second Dv50 to produce an activator composition,wherein the activator composition comprises a chemical composition comprising 40-80% w / w silicon dioxide, and 10-40% aluminium oxide, and wherein the first and second Dv50 particle size differs by at least 10pm.In one example the method comprises applying an electrostatic charge to the activator composition. In one example, electrostatic charge is applied by way of the power delivery of at least 0.1 to 0.6 kWh / kg of activator powder.

[0166] As will be appreciated by the above examples, the unexpected efficacy of the activator when combined with other concrete components is at least partially determined by the chemical and physical properties of the pozzolan component and the activator composition. The pozzolan component may be produced by combining one pozzolan compound with at least one other pozzolan compound to result in the preferred properties described.

[0167] In one example, preparation of the pozzolanic component of the activator composition, for example the method and activator of the preceding paragraph, may further comprise the steps of:a. identifying a chemical composition of at least two pozzolans;b. calculating the required amount of pozzolan a first pozzolan and a second pozzolan to achieve a chemical composition of the pozzolan component in a pre-determined range;c. combining the calculated amounts of pozzolans to produce an activator.

[0168] The ways in which pozzolan compounds can be selected and combined to result in the inventive compositions are able to be readily determined by those of skill in the art, in accordance with standard testing and combinatorial procedures. Those of skill in the artwould calculate the requisite amount of corresponding pozzolan materials to achieve a pozzolan component within the prescribed range of chemical compositions described herein.

[0169] Although admixtures are typically provided in a liquid form, it is preferable to formulate and store the activators of the invention when in a dry powdered form. For example, the moisture content of the components or portions of the activator should preferably result in an activator with a moisture content of less than 5%. Moisture content can be measured according to standard methods known to those of skill in the art.

[0170] If the moisture content is too high, for example 5% or over, the formulation machinery can malfunction and block due to machinery becoming fouled, especially air pumps designed to transport dry material thorough tubes. Further, when a plasticiser or superplasticiser is used in the activator composition, this component can react with water and partially set or reduce effective surface area of the activator components. This results in decreased efficiency of binding, and difficulty in storage or transportation of the activator prior to concrete formulation.

[0171] To achieve the desired moisture content, components of the activator may require drying according to known processes. One unexpected advantage of using pozzolans for the preparation of an activator is that it can be dried if the moisture content rises to be too high, for example over 5%, or 3% depending on the application and stability of the product required. In contrast, cement-containing compositions bind to each other and cannot be used if the material gets wet or beyond a threshold moisture content.

[0172] In one example, the activator comprises pozzolan portions which each comprise a moisture content of less than about 5%. In a further example, the pozzolan portions each comprise a moisture content of less than about 3%.

[0173] In one example, the activator comprises a moisture content of less than about 5%. In a further example, the activator comprises a moisture content of less than about 3%.

[0174] The moisture content may be adjusted to be within this range, or maintained within this range if material obtained is already at the desired moisture content.

[0175] The invention described herein comprises an activator comprising a natural or synthetic pozzolan that may have a multi-modal particle size distribution. In one example, the multi-modal distribution comprises at least two distinct peaks of particle size frequency or volume density - i.e. a bi-modal distribution as shown in the figures. In another example, the multi-modal distribution comprises at least three distinct peaks of particle size frequency - i.e. a tri-modal distribution. In some examples, the distribution comprises a multi-modal distribution which is defined as more than two distinct peaks of particle size frequency. For example 4, 5, 6, 7, 8, 9 or 10 distinct peaks.

[0176] In one aspect, the invention provides an activator admixture for producing concrete, the activator comprising a pozzolan component and a plasticiser component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes.

[0177] In one example the multi-modal particle size distribution is achieved by adding two or more pozzolan portions, wherein each pozzolan has a Dv50 different to every other pozzolan portion. In one example, the Dv50 differs by at least 10pm. Although the Dv50 of distinct portions used to formulate the pozzolan component will be different, it will be appreciated that the resultant pozzolan component found in the activator will have mixed portions. Therefore the pozzolan component will have a single Dv50 median particle size but portions with distinct particle size distributions, the median particle size of which can be measured and reported separately. Where particle size analysis indicates that there are distinct particle size distribution peaks (for example in the particle size volume density graphs shown in the figures), these peaks can be attributed as being the original Dv50 values of the pozzolan portions combined to produce the pozzolan component. The difference between the distinct Dv50 values indicates that different particle sizes are present in the composition.

[0178] The particle size distributions of the present invention provide unique reactive properties and strength. Without wishing to be bound by theory, it is believed that this enhancement is at least partially explained by the different particle size portions filling interstitial spaces within the other portions to provide an enhanced matrix and therefore enhanced strength. For example, particles from a first pozzolan portion fills at least a plurality of interstices between particles of at least one of a second pozzolan portion and a third pozzolan portion. In some examples, particles of a second portion of particles fills at least a plurality of interstices between a third portion of particles. This unique arrangement of particles contributes to the water resistance, durability, and tensile and compressive strength of the resultant mortar or concrete as observed in the examples. The portions of pozzolan particles described herein may be from natural pozzolans, each with a different chemical composition.

[0179] As will be understood by those of skill in the art, the particle size of each particle of a composition will vary about a mean. In some examples, the median of the volume distribution is used to describe the particle size and is referred to as "Dv50" or D(v,0.5). This parameter describes the maximum particle diameter below which 50% of the sample volume exists - also known as the median particle size by volume.

[0180] To determine the Dv50, a sample of the material is analysed using a particle size analysis technique. Such techniques will be known to those of skill in the art but by way of example, they may be selected from sieve analysis, laser diffraction, and sedimentation.Alternatively, the particle size may be defined in terms of size and volume density at that size (for example see tables in example 1 and 2 derived according to Test protocol 3).

[0181] In the examples described herein, the activator comprises a portion of pozzolan particles comprising a coarse particle size, and a second portion of pozzolan particles comprising an intermediate particle size. In one example, activators described herein may further comprise a third portion of pozzolan particles comprising a fine particle size.

[0182] Examples la, lb, 1c, 2a, 2b, 5 and 6 provide example of activators comprising at least bi-modal particle size distributions. Each activator provides enhanced concrete properties (strength and / or workability) compared to control mixes. The activators described may also include a plasticiser. In some examples, the plasticiser comprises a particle size of 100-200pm. This component of the activator can be observed in the volume density graphs for the examples as a minor peak above 100pm.

[0183] The inventors have found that a controlled particle size distribution of natural or synthetic pozzolans included within the activator increases the reactivity of limestonecontaining cementitious systems. The presence of multiple particle size fractions enhances particle packing. The presence of multiple particle size fractions increases reactive surface area available for hydration reactions.

[0184] The activator may be incorporated at between 0.25-10% by weight of cementitious material. The activator may be incorporated at between 0.5-8% by weight of cementitious material. The activator may be incorporated at between 1-4% by weight of cementitious material.

[0185] In certain examples, incorporation of the activator within these ranges results in increased early-age strength development. In certain examples, incorporation of the activator results in increased later-age compressive strength. In certain examples, incorporation of the activator results in improved durability. In certain examples, incorporation of the activator results in improved workability retention compared with limestone-containing systems without activator.

[0186] In some examples, the specific surface area (SSA) of the activator admixture comprises between 350-1000m2 / kg. It will be appreciated by those of skill in the art that the SSA of an admixture, particularly when incorporating pozzolans into concrete, significantly influences both the speed of setting and the strength development of the concrete. The inventors have found that the use of porous particles and a portion of particles of intermediate size (i.e. 0.5-1.5pm) increases the reactive surface area, thereby accelerating the pozzolanic reaction with calcium hydroxide during cement hydration. Fine particles (i.e. less than about 0.3pm) are not required to achieve the benefits of the activators described herein. This enhanced reactivity leads to a faster setting time and contributes to early strength gain. Additionally, the higher SSA achieved by porous particles can increase the water demand as these particles absorb more water. The activatoradmixtures of the invention balance this increased water demand with a plasticiser (water reducer) provided at pre-determined concentrations to ensure that the absorption is balanced by availability of free water for cement hydration. This avoids the undue stiffening of the mix. This balance is exemplified in the examples provided below where the slump (workability) of the activator containing mixes is maintained at a level substantially equivalent to mixes not including activator. This balance ensures that workability and early strength are provided as features of the concrete produced using the activator admixtures of the invention.

[0187] In one example, the invention comprises a pozzolan component comprising a mixture wherein at least 90% of particles comprise a particle size between 1 - 180pm. In one example at least 50% of the volume of particles of the pozzolan component comprise less than 40pm i.e. (Dv5040pm). In another example at least 50% of the volume of particles of the pozzolan component comprise less than 50pm i.e. (Dv50 50pm). In another example the activator may comprise a Dv50 of from 10 to 50pm). As referred to herein, a "pozzolan component" means the part of the activator composition which is made from pozzolanic compounds i.e. not including plasticiser or any other added, non-pozzolan components.

[0188] In one example, the activator comprises a pozzolan component comprising at least two pozzolan portions. In some examples, the activator may comprise a third or further pozzolan with the same or different Dv50. The proportions of the pozzolans can be adjusted by those of skill in the art to achieve the particle size distribution described below. In one example, the particle size distribution comprises:• 15-55% of particles are less than 15 pm;• 50-80% of particles are less than 40 pm; and• 70-100% of particles are less than 90 pm.

[0189] In a further example, the particle size distribution comprises:• 30-40% of the activator comprises particles less than 15 pm,• 50-65% of the activator comprises particles less than 40 pm,• 75-90% of the activator comprises particles less than 90 pm.

[0190] Example la describes an activator (Gamma) comprising natural pozzolans wherein the activator comprises a Dv50 of about 24.2pm, particle size less than 15 pm made up about 38%, particles less than 40 pm made up about 65%, and particles less than 90 pm made up about 90%.

[0191] Example lb describes an activator (Omega2) comprising natural pozzolans wherein the activator comprises a Dv50 of about 31pm, particle size less than 15 pm made up 34%, particles less than 40 pm made up 55%, and particles less than 90 pm made up 78%.

[0192] In a further aspect, the invention provides a method of producing an activator for use as an admixture for concrete comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a first particle size Dv50,b. obtaining a second pozzolan portion with a second chemical composition and a second particle size Dv50;c. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;d. mixing the pozzolan component with a plasticiser to produce the activator.In one example the plasticiser comprises a powdered plasticiser.

[0193] In one example, the mixing step is carried out for a period of at least five minutes.

[0194] In one example, the activator comprises an intermediate particle size and a coarse particle size. In one example the intermediate particle size peak is in a range of 0.5-1.5pm and the coarse particle size peak is in a range between 10-80pm. The examples illustrate this property of the activators of the invention whereby a volume density peak corresponding to intermediate particles is observed in a range of 0.5-1.5pm and the coarse particle size peak comprises a range between 10-80pm. The first pozzolan component exhibits a volume density peak of between 0.3 and 1.5% for particles at between 0.5pm and 1.5pm and a second pozzolan component exhibits a volume density peak of greater than 3% between 10 and 80pm. In some examples, a volume density ratio of a first peak to a second peak comprises 1:2 to 1:30, preferably 1:3 to 1:8, wherein the peaks may correspond to the first and second pozzolan portions. These peak ranges may correspond to the Dv50 values of a first and second pozzolan portion.

[0195] Accordingly, in one example relating to a concrete mix comprising limestone, the activator comprises a first pozzolan portion having an intermediate particle size in the range of 0.5-1.5 pm and a second pozzolan portion having a coarse particle size in the range of 10-80 pm. In another example, the activator comprises a first pozzolan portion exhibiting a volume density peak of between 0.3 and 1.5% for particles at between 0.5 pm and 1.5 pm, and a second pozzolan portion exhibiting a volume density peak of greater than 3% between 10 pm and 80 pm. When incorporated into a limestone-containing cementitious mix, this combination of particle sizes enhances both particle packing and chemical interaction within the binder matrix.

[0196] As referred to herein, a "volume density peak" refers to a local maximum in the differential particle size distribution curve, for example when particle size is measured using laser diffraction techniques. The particle size distribution is determined as a function ofparticle diameter and expressed as percentage volume of particles within discrete size intervals. A volume density peak corresponds to a particle size region in which the differential volume percentage reaches a local maximum relative to adjacent particle size intervals. Particle size measurements, including DvlO, Dv50 and Dv90 values and differential volume density distributions, may be determined using methods known to those of skill in the art, for example laser diffraction analysis in accordance with standard practice. In certain examples, measurements are performed using a laser diffraction particle size analyser under dry dispersion or wet dispersion conditions, as appropriate for the material being analysed.

[0197] In examples where two or more volume density peaks are present, the peaks correspond to distinct particle size fractions within the pozzolan component. Such peaks may represent intermediate and coarse particle size regions, respectively, and may be separated by a relative minimum in the differential volume distribution curve.

[0198] In mixes comprising limestone as a partial cement replacement or addition, interstitial filling becomes particularly important due to the altered particle packing and reduced cement content. The presence of intermediate-sized activator particles enables effective filling of voids between larger cement grains, limestone particles and aggregate. Where the activator further comprises a powdered plasticiser, the intermediate particles assist dispersion and improve packing density. This improved microstructural arrangement reduces capillary void content, enhances workability and compaction, and contributes to improved early-age strength development in limestone-containing systems.

[0199] In examples where the mixing step is carried out for a period of at least five minutes, extended mixing promotes uniform distribution of both intermediate and coarse activator particles throughout the limestone-containing mix. Uniform dispersion is particularly beneficial in blends where limestone is present at 10-25% by weight of cementitious material, as it facilitates consistent interaction between the activator, cement hydrates and carbonate phases. This results in a more homogeneous binder structure and reduces the risk of localised weakness associated with limestone substitution.

[0200] In limestone-containing mixes comprising an activator with an intermediate particle size peak between 0.5-1.5 pm and a coarse particle size peak between 10-80 pm, the combination of particle sizes facilitates optimal interstitial filling and enhanced chemical reactivity. The intermediate particles occupy void spaces between coarser particles, while the chemically distinct pozzolan portions participate in hydration reactions. The resulting dense microstructure reduces porosity and permeability and improves compressive strength development relative to comparable limestone mixes without the activator. The examples demonstrate that the activator mitigates the strength reduction typically associated with limestone substitution and, in certain formulations, enables early-age strength performance comparable to or exceeding reference mixes without limestone.

[0201] Plasticisers, "water reducers", or "superplasticisers" are chemical compounds used in concrete to improve the workability of fresh concrete. When added to the concrete mixture, plasticisers reduce the amount of water required for proper workability, which helps to improve the strength and durability of the concrete by reducing water-cement ratio and minimising porosity, cracking, and shrinkage. Unless the mix is "starved" of water, the strength of concrete is inversely proportional to the amount of water added or watercement (w / c) ratio. Therefore, in order to produce stronger concrete, less water is added. To avoid "starving" the mix, it may be necessary to use plasticisers or superplasticisers.

[0202] Plasticisers work by adsorbing onto the binder (e.g., cement) particles and creating a repulsive force between them, which helps disperse the particles and reduce the viscosity of the mixture. This results in a more fluid and cohesive concrete mixture that can be easily moulded or placed without segregation or bleeding.

[0203] Different types of plasticisers are available, including lignosulfonates, sulfonated melamine formaldehyde condensates, naphthalene sulfonate formaldehyde condensates, and polycarboxylates. Each type of plasticiser has its own specific properties and benefits, and the selection of a plasticiser depends on the required workability, strength, and durability of the concrete mixture.

[0204] In one example, the activator comprises a plasticiser. The inventors have found that the plasticiser and a pozzolanic mix with defined properties (particle size distribution and chemical composition) together create a synergistic effect that results in speeding up the pozzolanic reaction in concrete by two to three times. As a result, concrete containing activator comprising plasticiser plus pozzolans gains strength faster at each age of strength setting.

[0205] Accordingly, in some examples, the activator admixture described herein comprises at least one of: a polycarboxylate plasticiser; a naphthalene plasticiser, a superplasticiser; a lignosulphonate plasticiser; a dry form plasticiser; and a dry powder polycarboxylate superplasticiser.

[0206] In one example, the activator according to the present invention comprises a polycarboxylate (PCE) plasticiser. Use of pozzolans in the activator can also increase viscosity of the mix and can reduce workability. Therefore, to counteract this effect, the activators of the present invention may comprise a plasticiser.

[0207] Plasticisers also include superplasticisers or "high range water reducers".Superplasticisers provide a higher rate of water reduction while maintaining strength. In one example, the plasticiser used in the activators described in herein is a superplasticiser, otherwise known as a high range water reducer. Although the activators of the invention may be prepared without a plasticiser, it will be appreciated that this will significantly reduce the workability due to the limited ability to reduce water. Strength would also be compromised in mixes without plasticisers. The activators described herein may beprepared without a plasticiser which is then added subsequently by the concrete formulator rather than the activator manufacturer. This is particularly the case where specialised plasticisers are required, for example for underwater structures, high strength structures, or corrosion resistant concrete.

[0208] In many examples of concrete mixtures, liquid plasticisers are added. The inventors have however found that the activator compositions of the present invention show particular efficacy when a plasticiser in dry form is used. In one example, the plasticiser of any activator or concrete mixture described herein comprises a dry powder plasticiser. In this example, the plasticiser may comprise a polycarboxylate plasticiser. The plasticiser may comprise a superplasticiser and may be a polycarboxylate superplasticiser, again preferably in dry powdered form. Dry powdered format plasticiser comes in the form of granules or powder, which can be easily measured, stored, and mixed with other concrete ingredients. In contrast, liquid plasticisers can be messy to handle and may require special containers or precautions for storage and transportation. In addition, powdered plasticisers provide advantages in being able to blend with the dry format pozzolans and disperse evenly throughout the mixture. They enable the preparation of the activator without having to measure and handle liquids during concrete preparation. The powdered format plasticisers offer better control over dosage compared to liquid plasticisers. They are also easier to measure and enable adjustment of the amount of dry powder plasticiser added to the concrete mix, ensuring precise and consistent results. Liquid plasticisers, on the other hand, can be more difficult to measure accurately, leading to variations in the plasticising effect.

[0209] In one example, the activator comprises a plasticiser at a percentage (w / w) of from about 8% to 40% or 10% to about 40%. In some examples, this range is about 10% to about 25%, depending on types of pozzolans and the required purpose of the concrete. In another example, the activator comprises a ratio of pozzolan component to plasticiser at a ratio of from 11:1 to 1.5:1, or 9:1 to 1.5:1 or 9:1 pozzola plasticiser to about 3:1 pozzolan: plasticiser. In another example, the plasticiser is added to the activator at 8-40% w / w of the activator. It will be appreciated by those of skill in the art that the addition of plasticiser at such high concentrations in the activator admixture is a clear indicator that the activator is not a major portion of the concrete mixture; instead, it represents a minor proportion of the concrete composition.

[0210] It is desirable for the plasticiser to be prepared with a weight average particle size which achieves maximum efficacy in adsorbing onto, and mixing with the natural pozzolan portions of the activator. To achieve these improvements in reaction efficiency and mixing, in one example, the plasticiser present in the activator has a Dv50 of from about 50-500pm. In another example, the plasticiser present in the activator has a Dv50 of from about 100-200pm.

[0211] In one example, there is provided an activator for use as an admixture for concrete comprising:a) a pozzolan component comprising at least two pozzolans comprising distinct particle sizes and chemical compositions; andb) a powdered plasticiser with a particle size from 50-500pm;wherein the pozzolan component and plasticiser have been mixed for over 5 minutes.Effective mixing of the activator components is required to provide a stable admixture composition for addition to other concrete components.

[0212] There is a prevailing view in the art that pozzolanic concrete has slower strength gain, especially early strength development when compared to ordinary concrete prepared using Ordinary Portland Cement (OPC). Typically, ordinary concrete (using OPC) exhibits faster early strength development within the first few days after casting. This is due to the rapid hydration reaction of the Portland cement. Pozzolanic concrete has in the past been associated with slower early strength development because the pozzolanic reaction is slower to start. The pozzolanic materials react with calcium hydroxide (a byproduct of cement hydration) to form additional calcium silicate hydrate (C-S-H), but this process takes more time to initiate compared to the hydration of OPC.

[0213] The inventors have found that the powdered activators of the invention comprising a combination of components including a plasticiser and a pozzolanic mix with properties referred to herein, (for example particle size distribution, specific surface area, electrostatic charge and chemical composition) together create a synergistic effect that is achieved through interaction of the plasticiser and pozzolans, and pozzolans with each other. This speeds up the pozzolanic reaction in concrete by two to three times and the strength of concrete containing activator as an admixture is accelerated at each age of strength setting. Further, the final strength of concrete containing activator is higher than that of concrete without the activator.

[0214] The synergistic effect further creates denser packing of particles achieved by the interaction of the plasticiser and pozzolans, and pozzolans with each other which leads to increased strength and durability of the hardened concrete. The additional reactive cementitious compounds formed through pozzolanic reactions contribute to improved compressive strength, reduced permeability, and enhanced resistance to chemical attack. Thus, both chemical and mechanical properties of pozzolans are important to achieve the synergistic effect and improve hardened concrete or mortar properties.

[0215] Another example of the efficacy and synergism of the activators described herein is that relatively small quantities of activator may enable substantial cement reduction in limestone-containing concrete compositions. The activator may be incorporated at between 0.25-10% by weight of cementitious material. The activator may be incorporated at between 0.5-8% by weight of cementitious material. The activator may be incorporated atbetween 1-4% by weight of cementitious material. Within these ranges, cement content may be reduced by between 20-50% relative to a reference concrete composition without activator. In certain examples, compressive strength at measured timepoints is maintained despite such cement reduction.

[0216] Another example of the efficacy and synergism of the activator is observed in concrete compositions containing limestone and / or natural or synthetic pozzolans as filler components. In such systems, incorporation of the activator enables cement reduction of at least 30% relative to a standard concrete mix without activator. In certain examples, cement reduction of greater than 30% is achieved. In certain examples, cement reduction of up to 40% is achieved. These reductions may be achieved while maintaining structural performance requirements.

[0217] By way of illustrative example, a 20 MPa concrete mixture may conventionally require approximately 250 kg of cement acting as the primary binder. In an illustrative embodiment, approximately 30% of the cement (about 75 kg) may be removed. An activator may then be incorporated at a dosage selected within the ranges described herein, for example between 0.25-10% by weight of the remaining cementitious material. Where approximately 175 kg of cement remains, an activator dosage of approximately 2.5-7 kg corresponds to a range of approximately 1-4%. The remaining mass corresponding to the removed cement may be replaced with substantially inactive filler, such as aggregate and / or sand, and / or supplementary cementitious materials. In such illustrative examples, embodied carbon emissions of the resulting concrete composition are reduced due to the reduction in clinker content.

[0218] Example 1c demonstrates this effect using an activator "Pi" containing a specific particle size distribution of natural pozzolans. The cement used in the "control 2" mix is 386kg / m3compared to 275kg / m3in the activator mix - a 28.8% reduction in cement mass. The bulk of the concrete is made up by inactive filler - i.e. aggregate. The concrete strength as shown in Figure l.c.ii is substantially the same at day 1,3,7 and 28 for the activator and control mixes.

[0219] Also in example 2a (Figure 2.a.ii), when the same amount of cement is included in the control and the activator mix (see control 1 - 275kg / m3), the strength of the concrete is increased in the activator mix - day 1= 240% stronger, day 3= 187% stronger, day 7= 163% stronger, day 28= 145% stronger.

[0220] The reduced-cement concrete mixture also exhibits enhances flowability, cohesiveness, and stability, making the mix easier to pump, place, and finish. This is particularly beneficial in large-scale construction projects where concrete needs to be transported over long distances or in challenging environments.

[0221] Measuring the chemical composition of a natural pozzolan is an important step in determining its suitability for use in concrete activators. A representative sample of thenatural pozzolan is prepared for analysis which may involve drying the sample and grinding it to a fine powder to ensure homogeneity. Several methods for measuring the chemical composition of natural pozzolans will be known to those of skill in the art. These include X-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX).• XRF is a commonly used technique because it is fast, accurate, and can analyze a wide range of elements. In this method, a sample of the natural pozzolan is bombarded with X-rays, causing the atoms in the sample to emit characteristic fluorescent X-rays. The energy and intensity of these X-rays are detected and analyzed to determine the elemental composition of the sample.• Atomic absorption spectroscopy (AAS) involves vaporizing the sample and passing a beam of light through the vapor. The absorption of the light by the sample is proportional to the concentration of the element being analyzed, allowing for quantitative analysis of the element.• Inductively coupled plasma-optical emission spectroscopy (ICP-OES) involves vaporizing the sample in an argon plasma and analyzing the light emitted by the excited atoms using a spectrometer. The intensity of the emitted light is proportional to the concentration of the element being analyzed.• Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) is a microscopy technique that involves viewing the natural pozzolan particles under a microscope and measuring the X-rays emitted by the atoms in the sample. The chemical composition of the sample can be determined by analyzing the X-ray spectra.

[0222] Once the chemical composition data has been obtained, it can be analyzed using statistical software to determine the concentrations of different elements and their relative proportions. The results are then used to evaluate the quality of the natural pozzolan and optimize its use in concrete mixtures.

[0223] Measuring the particle size distribution of natural pozzolans is an important step in determining their suitability for use in concrete, as well as their potential performance in terms of strength, durability, workability, and aesthetics. Several methods for measurement of particle size and particle size distribution will be known to those of skill in the art. A first step is to prepare a sample of natural pozzolan for analysis. This typically involves taking a representative sample of the natural pozzolan and drying and sieving the sample to remove any impurities or oversized particles.

[0224] There are several methods available for measuring particle size distribution, including laser diffraction, sedimentation, and microscopy.• Laser diffraction is a commonly used technique because it is fast, accurate, and can measure a wide range of particle sizes. In laser diffraction, the natural pozzolan sample is dispersed in a liquid medium, such as water or alcohol, and passed through a laser beam. The laser light is scattered by the particles in the sample, and the scattering pattern is captured by a detector. The intensity of the scattered light is related to the size of the particles, and the distribution of sizes is calculated using mathematical algorithms.• Sedimentation: In sedimentation analysis, the natural pozzolan sample is dispersed in a liquid medium and allowed to settle under gravity. The settling rate of the particles is related to their size, and the particle size distribution is calculated using mathematical equations.• Microscopy: Microscopy techniques involve viewing the natural pozzolan particles under a microscope and measuring their size manually. This method can be timeconsuming and labour-intensive but can provide high-resolution images and accurate measurements.

[0225] Once the particle size distribution data has been obtained, it can be analysed using statistical software to determine the mean particle size, the spread of the distribution, and other parameters that may be of interest.

[0226] In one example, activators of the present invention may be prepared using the following steps:1. Measurement of moisture content of each pozzolan portion and adjustment to be less than 5%. Alternatively, the moisture content of the pozzolan mixture may be adjusted to be less than 3%. This preferred range of moisture content enables the mixing and storage of the components and to ensure there is substantially no water in the mix to react with the plasticiser in the Activator.2. Chemical composition analysis and amendment - pozzolans (also referred to herein as pozzolanic material) are analysed to identify their chemical composition. The percentage by weight or molar concentration of each chemical compound of interest is determined in each pozzolanic material. The proportions of different pozzolans are then amended to achieve the required chemical composition (within the ranges specified herein).3. Particle size determination and amendment - The particle size is adjusted to be in a specified range for each pozzolan of a specified chemical composition. Larger pozzolan particles may be size-reduced e.g. by grinding to form a ground pozzolan mixture of a particular particle size. The ground pozzolan may be obtained as a waste "side-stream" from larger pozzolan rocks used for other purposes.4. Measurement of particle size distribution and amendment if necessary - The distribution of particle sizes is important to balance the reactivity and setting speed of the concrete. The distribution is controlled by combining pozzolan sources with known particle sizedistribution with other sources to provide a required distribution comprising polydisperse particle sizes.5. Mixing of activator components and a plasticiser in required proportion - the activator components referred to herein are mixed in a suitable mixing apparatus. This mixing step should be carried out for at least 5 minutes to achieve sufficient mixing of the different activator components. A further processing step of grinding, for example in a ball mill is undesirable because it results in an inconsistent particle size reduction (i.e. larger particles will be size reduced to a larger extent than smaller particles which can upset the balance of particle size distribution in the activator product. This further grinding step also increases energy demand and concomitant embodied carbon.

[0227] In one example, the activator is in a liquid form. In this example, the method of preparation comprises mixing the dry activator mixed with a suitable solvent, for example water, at an appropriate ratio for storage, transport and final formulation with other concrete components. In one example, the liquid activator is formulated with the solvent at a w / w ratio of activator: solvent about 1:2, about 1:1, about 2:1.

[0228] A key advantage of using a dry form activator is to maintain a stable activator: solvent ratio on preparation. Where liquid forms of the activator are prepared, for example according to the above formulations, the activator: solvent ratio may change due to evaporation of the solvent, or settling of active components and incorrect mixing prior to final formulation.

[0229] In some embodiments, the activator components are blended without intergrinding. Intergrinding in this context refers to the grinding of various components to effect particle size homogenisation, reduction and mixing. Intergrinding the components is energetically costly which can increase the overall carbon emissions. The presently provided activators of the invention may comprise components that are blended rather than interground.

[0230] Heating of the activator components is energetically costly which can increase overall carbon emissions associated with production of concrete. The present invention does not require thermal treatment of the activator. Therefore in some examples described herein, the activator is not heated prior to mixing.

[0231] Concrete is composed of three key components - aggregates, cement and water. Admixtures including plasticisers are also used most of the time. Aggregate provides mechanical stability by acting as a filler material, binding the cement paste together and forming a solid matrix. The strong interlocking nature of aggregates enhances the overall compressive strength and load-bearing capacity of concrete structures. Since aggregates occupy a significant volume in concrete, they help to reduce the cost by replacing cement with aggregates.

[0232] Aggregates are described herein as coarse or fine. Coarse aggregates are particulates that are greater than about 4.75mm. The usual range employed is between 9.5mm and 37.5mm in diameter. Fine aggregates are usually sand or crushed stone that are less than 9.55mm in diameter. Typically, the most common size of aggregate used in construction is 20mm. A larger size, 40mm, is more common in mass concrete.

[0233] One form of fine aggregate is sand. Sand is a granular material composed of small particles with a particle size ranging from 0.0625 mm to 2mm in diameter. In its natural form, it is found in various geological formations, such as riverbeds, beaches, deserts, and quarries. As a fine aggregate in concrete, it fills the voids between larger aggregates to enhance the workability and cohesiveness of the concrete mix. Those of skill in the art will appreciate that the term "sand" also encompasses fine aggregates that are not of mineral origin such as sand substitutes. These include, for example, manufactured sand, washed bottom ash, glass powder or quarry dust. Sand is a relatively inexpensive and available component compared to other concrete components. In some examples of the invention provided herein, cement is replaced with sand, coarse aggregates plus activator to make up the solids proportion when using lower cement proportion. Sand also has a much lower carbon footprint than cement, is cheaper and requires less processing.

[0234] Water plays a vital role in hydrating the cement to form a strong and durable binder. This binder acts to bind the aggregates and sand together and hardens over time, creating a solid and cohesive structure. Water reacts with plasticisers to modify the rheology and flow characteristics of the concrete. Water is also involved in the curing process, where it helps maintain the necessary moisture levels for proper cement hydration and strength development. The water-to-cement (w / c) ratio is a critical parameter that affects the strength, durability, and overall performance of concrete. It represents the amount of water relative to the amount of cement in the mixture. The w / c ratio should be carefully controlled to achieve the desired strength while maintaining adequate workability and durability. An excessive water content can weaken the concrete and lead to increased porosity, reduced strength, and increased permeability.

[0235] In one example the activators of the invention allow a reduction in water usage compared to preparation of concrete without activators (but with plasticisers or water reducers). The water reduction achieved with the activator can range between 10-45%, as compared to control concrete with and without the plasticisers / water reducers. On top of contributing to strength increase in concrete, this feature of the activator has particular utility in environments where water is scarce, or where substantial water usage is undesirable (e.g. for cost factors).

[0236] In one example the cementitious materials in the binder are selected from Portland cement and supplementary cementitious materials.

[0237] Supplementary Cementitious Materials (SCMs) are finely divided materials that are used in conjunction with Portland cement in concrete or mortar mixtures. The proportion of SCMs in a concrete mix is however limited by the inherently unreactive properties of most SCMs. Some SCMs are used as non-reactive fillers rather than reactive components. Where high substitutions of SCMs are attempted in concrete mixtures, substandard concrete properties are observed such as reduced compressive strength, reduced durability, increased setting time and reduced workability.

[0238] In one example, SCMs comprise natural pozzolans e.g. pumice, fly ash, slag, silica fume, metakaolin (thermally activated kaolin clay), and rice husk ash. Natural Pozzolans are also used as SCMs but sometimes presented as fillers, rather than active components.SCMs may further comprise a material selected from the group consisting of Trass flour, recycled glass, fly ash, bottom ash, cenospheres, glass bubbles, slag, clays, calcined clays, partially calcined clays, kaolinite clays, lateritic clays, illite clays, crystalline silica, silica flour, cement kiln dust, volcanic rock, natural pozzolans, mine tailings, diatomaceous earth, zeolite, shale, ground vitrified pipe, agricultural waste ash, ground granulated blast furnace slag, bentonite, pumice, and any combination thereof. In some examples, the activator admixtures of the invention are provided in combination with one or more pozzolan SCMs. In these examples, the activator activates the SCM to provide an SCM with enhanced reactivity versus the SCM alone. This important effect of the activators of the invention is shown in example 8 and 10 and enables cement (high embodied carbon) to be replaced by SCMs (lower embodied carbon) without losing the binding capability that is typically observed when substituting cement with SCMs.

[0239] Portland cement is a manufactured material produced via a process called clinkerisation, which involves heating a mixture of limestone, clay, and other minor ingredients at high temperatures. The resulting clinker is then ground into a fine powder, which is known as Portland cement. The chemical composition of Portland cement primarily consists of calcium silicates, including tricalcium silicate and dicalcium silicate. These compounds are responsible for the cement's ability to harden and gain strength through hydration when mixed with water. Other compounds, such as calcium aluminate, calcium sulfate (gypsum), and minor additives, may also be present, depending on the specific cement type. In some examples, the cementitious material comprises a Portland cement suitable for wells. Portland cements that are suited for use in the disclosed compositions include, but are not limited to, API Class A, C, G, H, low sulphate resistant cements, medium sulphate resistant cements, high sulphate resistant cements, other construction cements, or combinations thereof. The API class A, C, G, and H cements are classified according to API Specification 10. Additional examples of Portland cements suitable for use in the present disclose include, without limitation, those classified as ASTM Type I, II, III, IV, or V as described below. In some examples, the cementitious material comprises aclass C cement. In some examples, the cementitious material comprises a class G cement. For Portland cement types, ASTM C150 describes:;0240] When water is added to Portland cement, it undergoes a series of exothermic chemical reactions known as hydration. During hydration, the cement particles react with water, forming calcium silicate hydrate (C-S-H) gel and other compounds. This gel acts as a binder, binding the aggregates together to create a solid and durable concrete matrix.

[0241] Examples 1 and 2 relate to preparation of a concrete mix with compressive strength of 20, 25 and 40 MPa. The effects of the Activator and SCMs described in these examples are applicable to other concrete strengths. Those of skill in the art will be readily able to determine the respective modifications to the concrete mixes described herein to achieve concrete of different tensile strength. In one example, the invention provides activators and concrete formulations suitable for the production of 20MPa, 25MPa, 30MPa, 35MPa, 40MPa or 50MPa concrete. In general terms:20MPa concrete:• Non-structural applications such as levelling beds, pathways, and minor construction works. Foot traffic i.e. footpaths and house slabs25MPa concrete:• Residential Buildings for elements like footings, slabs, and non-structural walls. • Lightly Loaded Pavements: It can be used for pathways, driveways, and lightly trafficked areas where heavy loads are not expected.35MPA Concrete:• Residential and Commercial Construction: Grade 35 concrete is suitable for a wide range of applications, including foundations, beams, columns, and structural walls in both residential and commercial buildings.• Light Industrial Floors: It can be used for warehouse floors or light industrial facilities where moderate strength and durability are required.40MPA Concrete:• High-Rise Buildings: Grade 40 concrete is commonly used in the construction of tall buildings, providing the required strength for structural components like columns and cores.• Bridges and Infrastructure: It is suitable for bridge decks, piers, abutments, and other critical infrastructure components where higher strength and durability are necessary.• Heavy-Duty Industrial Floors: Grade 40 concrete is used in industrial settings with heavier loads and higher abrasion resistance requirements.50MPA Concrete:• High-Performance Structures: Grade 50 concrete is employed in structures where exceptional strength, durability, and resistance to aggressive environments are crucial, such as high-rise buildings, bridges, and marine structures.• Precast Elements: It is commonly used in the production of precast concrete elements, such as precast beams, columns, and panels, due to its high strength and early strength development.

[0242] The ratio of cement to aggregates is adjusted in higher grade concrete to provide a higher proportion of cement which contributes to achieving the increased strength.Cement is the binding agent in standard concrete, and it contributes significantly to its strength therefore higher cement content enables the product to withstand higher loads and stresses.

[0243] In some examples, the activator and associated inventions described herein enable higher grade concrete to be prepared using the same or lower amount of cement.

[0244] In other examples, the activator and associated inventions described herein enable concrete of the same grade to be prepared using a lower amount of cement compared to standard concrete mixtures.

[0245] The water-to-cement ratio may also be reduced at higher grades to ensure better hydration and strength development. The ratio of fine aggregate to coarse aggregate may be adjusted. Also, larger aggregate sizes are used for higher-grade concretes, while smaller aggregate sizes are used for lower-grade concretes. Lower-grade concretes (e.g. 20-25Mpa) typically use smaller aggregate sizes, such as fine sand and small-sized coarse aggregates. These sizes contribute to improved workability and better bonding between cement and aggregates. Moderate-Grade Concretes (e.g., 35MPA and 40MPA) use a balanced combination of fine and coarse aggregates. This helps achieve a good balance between workability and strength. The sizes of the aggregates are typically larger than those used in lower-grade concretes but not as large as in higher-grade concretes. Higher-Grade Concretes (e.g., 50MPA and above) incorporate larger aggregate sizes. Coarse aggregates with larger particle sizes are used to enhance the strength and load-bearing capacity of theconcrete. These larger aggregates provide greater interlocking and mechanical properties, resulting in a higher-strength concrete.

[0246] Concrete properties can be measured to ensure that the material is suitable for its intended use and meets the required standards and specifications. Specific measurements of concrete properties include:• Compressive strength - the ability of the material to resist compressive forces.Compressive strength is measured by subjecting a test specimen of concrete to compressive loads until it fails. The maximum load that the specimen can withstand is recorded as the compressive strength of the concrete (in kilo Newtons kNt or Mega Pascals MPa).• Tensile strength: This refers to the ability of concrete to resist tension or stretching forces. Tensile strength is typically much lower than compressive strength, and it can be measured using various test methods, such as the splitting test or the flexural test.• Durability: This refers to the ability of concrete to resist deterioration over time due to various factors such as exposure to moisture, chemicals, and freeze-thaw cycles. Durability can be measured using various test methods, such as the water absorption test, the sulphate resistance test, and the freeze-thaw resistance test.• Workability: This refers to the ease with which concrete can be mixed, placed, and finished. Workability can be measured using various test methods, such as the slump test, the flow test, and the compacting factor test.• Density: This refers to the mass per unit volume of concrete and is typically measured using a density meter or by calculating the mass and volume of a test specimen.

[0247] The time it takes for the concrete mixture to begin to stiffen and lose its workability is termed the setting time. The setting time of pozzolanic concrete is an important factor that can affect its overall performance and durability. In a construction setting, timeframes and costs can also be dictated by the setting time of the concrete. A longer setting time is often beneficial for pozzolanic concrete, as it can allow more time for the mixture to fully hydrate and for the pozzolan to react with the cement, resulting in a stronger and more durable final product. A longer setting time can also be beneficial for workability, allowing more time for the mixture to be properly placed and finished before it begins to set. This can be particularly important in large or complex construction projects where the concrete needs to be placed quickly and efficiently, but also needs to maintain its workability long enough to be properly finished.

[0248] In some circumstances, a shorter setting time can be beneficial, such as in colder weather or in applications where the concrete needs to be load-bearing or supporting weight quickly. The inventors have found that activators comprising pozzolans can actually result in a decrease in the initial setting time and therefore unexpectedly provide early strength.

[0249] The invention provides concrete compositions comprising activators and limestone as described herein. The concrete compositions may be prepared according to mixing processes known by those of skill in the art, and using equipment typically used in the art. Concrete compositions comprise at least a coarse aggregate, a fine aggregate and a binder. While those of skill in the art will be able to determine specific concrete mixtures according to the materials and application of the concrete, the following non-limiting examples provide ranges of concrete and activator components that may be present:

[0250] In one example, the coarse aggregate and fine aggregate combined comprise 60-80% of the composition.

[0251] In one example, the invention provides a concrete composition comprising:a. an activator;b. cementitious material; andc. aggregate.

[0252] As will be understood by those skilled in the art, the binder in a limestonecontaining concrete composition may be formed by combining the cementitious material with the activator described herein. The activator functions as a reactive minor component of the binder and contributes to overall binding performance.

[0253] The activator may be present at between 0.25-10% by weight of cementitious materials. The activator may be present at between 0.5-8% by weight of cementitious materials. The activator may be present at between 1-4% by weight of cementitious materials. In certain examples, the activator may be present at approximately 1%, 2%, 3% or 4% by weight of cementitious materials.

[0254] The activator in the above concrete composition may be an activator as described anywhere within the specification as an activator of the invention. In particular examples, the activator may comprise one or more properties selected form the group consisting of at least a bi-modal particle size, natural or synthetic pozzolans; a chemical composition comprising 40-80% silicon dioxide and 10-40% aluminium oxide; Dv50 of less than 40pm; or a particle size distribution defined by:a. 30-40% of the activator comprising particles less than 15 pm;b. 50-65% of the activator comprising particles less than 40 pm; and c. 75-90% of the activator comprising particles less than 90 pm.

[0255] In one example, the activator may comprise one or more properties selected form the group consisting of at least a bi-modal particle size, natural pozzolans; a chemical composition comprising 40-80% silicon dioxide and 10-40% aluminium oxide; Dv50 of less than 40pm; or a particle size distribution defined by:a. 30-40% of the activator comprising particles less than 15 pm;b. 50-65% of the activator comprising particles less than 50 pm; and c. 75-90% of the activator comprising particles less than 90 pm.The cement quantity is typically determined by the mass of cement in kg.

[0256] In one example, the invention provides a method of preparing a reduced cement concrete composition comprising:a. determining a quantity of cement required for a concrete mixture; b. reducing the cement quantity by a reduction factor to provide a reduced cement quantity;c. determining an activator quantity based on the reduction factor;d. determining a filler quantity based on the reduction factor;wherein the activator comprises an activator as described herein.

[0257] In one example, the reduction factor is selected from the group consisting of at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, or at least about 60%. In one example, the reduction factor is selected from the group consisting of <10%, <20%, <30%, <40%, <50% or <60%. In one example, the reduction factor is 10% to 50%

[0258] In one example, when the reduction factor is less than or equal to about 35%, the activator quantity comprises at least 3% w / w of total cementitious material. In another example, when the reduction factor comprises less than or equal to about 50%, the activator quantity comprises at least 3.5% w / w of total concrete composition.

[0259] In one example, the filler quantity comprises the difference between the cement quantity (i.e. the original quantity of cement required by the standard mix) and the reducedcement quantity, minus the activator quantity. This provides a method for the skilled person to reduce the quantity of cement used in a concrete mix by replacing it with filler and activator. In some examples, the activator admixture is added to the filler (such as limestone) before, during or after preparation of the concrete mixture. In such instances, the activator admixture has been shown to assist in the activation of previously inert filler materials to make them more reactive to provide enhanced early and late strength gain as shown in example 11.

[0260] In a further example, the method further comprises preparing a concrete mixture comprising the reduced cement quantity, the activator quantity and the filler quantity.

[0261] The one or more filler may be selected from the group consisting of SCMs, fly ash, slag, silica fume, metakaolin, rice husk ash, synthetic pozzolan, natural pozzolan, aggregate and / or sand.

[0262] In some examples, the invention provides a concrete composition comprising SCMs and an activator admixture. In some examples, up to 50% of cement is substituted with a binder which is a combination of activator plus natural or synthetic SCMs. For the avoidance of doubt, references herein to cement being "substituted" or "replaced" by a binder comprising activator and natural or synthetic supplementary cementitious materials (SCMs) are intended to describe the compositional structure of the cementitious material on a weight basis. In such examples, the cementitious material comprises natural or synthetic pozzolan supplementary cementitious material in an amount of at least 10% by weight of the total cementitious material. In certain examples, the cementitious material comprises at least 20%, at least 30%, at least 40%, or up to 50% by weight of natural or synthetic pozzolan supplementary cementitious material.

[0263] As used herein, substitution does not require any particular intent or mental act, but instead refers to the presence of supplementary cementitious material within the cementitious fraction at the stated proportion relative to the total cementitious material.

[0264] Figures 9A and 9B illustrate the invention showing the substitution of cement with a portion of SCMs plus activator. The proportions shown in these figures are exemplary and not to scale and not intended to limit the scope of the invention. Without wishing to be bound by theory, it is believed that when activator admixtures described herein are combined with pozzolanic SCMs and cement in the presence of water, the hydration and pozzolanic reactions synergise to produce more CSH and a high-performance hydraulic binder. This binder exhibits equivalent or greater strength and reduced porosity compared to standard concrete containing OPC. In particular, traditional pozzolanic mixtures exhibited slower strength development which made them less suitable for construction projects with tight timelines. The present invention provides admixtures that avoids this drawback by maximising the initial reactivity of the pozzolans to enable the true potential of pozzolanic concrete to be realised in a process that is energy-efficient and low in carbon emissions.This substitute binder has similar properties to cement but with significantly lower carbon emissions.

[0265] When the activator is combined with the SCMs, water and Ordinary Portland Cement, a series of reactions occur which augment the cement hydration reactions and create additional chemical bonds. This results in a similar strength gain and workability compared with OPC, and superior durability. In standard concrete (figure 9A), Ordinary Portland Cement (OPC) is combined with water and aggregate (sand or rocks). The OPC combines with water and undergoes the hydration reaction to form concrete. In 9B, the pozzolanic reaction is leveraged to provide a hybrid chemical process which combines the hydration reaction with the pozzolanic reaction. This hybrid reaction involves:a. the cement hydration reaction to produce calcium hydroxide (Ca(OH)2); and b. the pozzolanic reactions in which the Ca(OH)2 is hydrolysed and consumed in the pozzolanic reactions by reaction with SiO2 and AI2O3 in the presence of water. c. This reaction forms compounds possessing cementitious properties to augment the strength and durability of standard concrete.

[0266] When water is added to Ordinary Portland Cement it undergoes hydration, producing calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)2). Pozzolanic materials (SiO2 and AI2O3) in the mix react with calcium hydroxide to form additional C-S-H, which is the primary binding phase in concrete, responsible for its strength and durability. Therefore the pozzolanic components of the reaction generate additional C-S-H, contributing to a denser and more robust microstructure. This additional C-S-H fills the voids and pores within the concrete, reducing its porosity and permeability. This less permeable material is more resistant to environmental factors such as freeze-thaw cycles, sulphate attack, alkalisilica reaction and the ingress of harmful substances. Example 3 illustrates this reduction in porosity and permeability and shows how the activator admixtures contribute to these beneficial effects.

[0267] In some examples, the invention provides a concrete composition comprising SCMs and an activator admixture. In some examples, up to 50% of cement is substituted with a binder which is a combination of activator plus natural or synthetic SCMs. For example 10% may be replaced which provide moderate levels of carbon emission reduction and may be appropriate for concrete compositions that require high cement content. In other examples, 20%, 25% or 30% cement substitution may be used with pozzolanic SCMs replacing the cement. These provide higher levels of cement substitution for enhanced carbon emission reduction. Activators of the invention are active to ensure that strength is not appreciably affected at these substitution levels. In other examples, higher levels of cement substitution may be achieved, for example 40, 50 or 60% substitution. At these levels there are substantial benefits in the reduction of carbon emissions but concrete strength may be negatively affected at very high substitution levels. For some applications,the strength is less important. Further, SCMs which already exhibit high surface activation (e.g. fly ash) may be used as a substitute for the cement, and, in tandem with activator admixtures of the invention, these high levels of substitution can still provide high strength concrete compositions.

[0268] Accordingly, in some examples, the invention provides a concrete composition comprising:a. an activator admixture as described hereinb. cementitious material, andc. aggregate; andd. limestone.The aggregate may comprise a coarse aggregate and a fine aggregate. The concrete composition may be designed to exhibit a compressive strength determined in accordance with NZS3112 part 2 at day 28 is greater than 20MPa or 25MPa. In some examples the concrete composition comprises cement and pozzolanic SCM filler wherein the pozzolanic SCM filler is present in an amount of 10 to 50% w / w of cementitious material, for example up to 10%, up to 20%, up to 25%, up to 30%, up to 40% or up to 50% SCM.

[0269] As demonstrated in the limestone-containing concrete examples described herein, concrete compositions comprising cementitious material, limestone, and the activator admixture are capable of achieving structural-grade compressive strengths despite partial substitution of Portland cement with limestone. In the examples, limestone replacement levels of up to 30% by weight of cementitious material were evaluated in both binary and ternary blended systems. The resulting compositions developed compressive strengths of at least 20 MPa at 28 days, as determined in accordance with NZS 3112 Part 2.

[0270] The examples further demonstrate that limestone-containing compositions incorporating the activator admixture achieve compressive strengths of at least 25 MPa at 28 days, and in several tested formulations at least 30 MPa at 28 days, notwithstanding substantial cement reduction. In comparative limestone control compositions lacking the activator, reduced strength development was observed across all measured ages.Incorporation of the activator materially recovered and, in certain examples, exceeded the strength of corresponding non-activated limestone systems.

[0271] In particular, the examples show that 30% limestone replacement systems incorporating the activator achieved compressive strengths approaching or matching those of 100% cement controls at intermediate and later ages. In ternary systems comprising limestone and supplementary cementitious materials, activator-containing compositions achieved strength development equal to or exceeding full cement controls at 28 days. These results confirm that the activator enables structurally viable limestone-containing concrete compositions with 28-day strengths of at least 20 MPa, optionally at least 25 MPa, and in certain implementations at least 30 MPa.

[0272] Without wishing to be bound by theory, it is believed that the dual-pozzolan activator promotes increased reactivity of limestone within the cementitious matrix, enhances formation of carboaluminate phases, accelerates secondary hydration reactions, and refines pore structure. The examples support that these mechanisms collectively enable maintenance or enhancement of compressive strength despite significant limestone substitution, thereby facilitating reduced cement content while achieving structural performance thresholds of 20 MPa, 25 MPa, or 30 MPa at 28 days.

[0273] The activator admixture described herein may be defined independently of any particular concrete formulation. In certain implementations, the invention provides an activator admixture comprising a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, and wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions. The activator may optionally further comprise a plasticiser component and may exhibit a bi-modal, tri-modal or multi-modal particle size distribution as described in the examples. The activator may be provided as a dry powder composition suitable for storage, transport and subsequent incorporation into cementitious systems.

[0274] The examples relating to limestone-containing concrete demonstrate that the structural characteristics of the activator - including the presence of chemically distinct pozzolan portions and a defined multi-modal particle size distribution - materially enhance the reactivity of blended cement systems containing limestone. The performance improvements observed in the examples are not attributable solely to filler effects or water reduction, but arise from activation of carbonate-containing cementitious matrices.

[0275] Accordingly, in certain aspects, the activator may be defined structurally without limitation to a particular limestone content or binder formulation. In other aspects, the activator may be defined functionally as an activator admixture for use in enhancing strength development in concrete compositions comprising limestone. The examples demonstrate that incorporation of the activator materially improves compressive strength development in limestone-containing systems, including binary and ternary blends, and enables maintenance or enhancement of structural performance despite partial substitution of Portland cement with limestone.

[0276] In further aspects, the invention provides the use of the activator admixture in limestone-containing concrete compositions. The examples support use of an activator admixture comprising a first pozzolan portion and at least a second pozzolan portion, differing in particle size and chemical composition, for improving compressive strength in concrete compositions comprising limestone. The examples further support use of the activator for enabling higher limestone substitution levels while achieving compressive strengths of at least 20 MPa, optionally at least 25 MPa, and in certain implementations at least 30 MPa at 28 days.

[0277] Without wishing to be bound by theory, it is believed that the activator promotes increased dissolution and reactivity of calcium carbonate phases, enhances formation of carboaluminate hydrates, accelerates secondary hydration reactions, and refines pore structure. The activator therefore constitutes a distinct and patentable composition per se, and also a composition suitable for use in enhancing performance of limestone-containing cementitious systems.

[0278] Limestone used in the present invention may be selected from natural limestone, processed limestone, ground limestone, or precipitated calcium carbonate, depending on the desired performance characteristics of the concrete composition. Natural limestone refers to quarried calcium carbonate rock that may undergo minimal processing, such as crushing and screening, to achieve the required particle size distribution. Processed limestone includes thermally or chemically treated forms, such as calcined limestone, which may exhibit enhanced reactivity in cementitious systems. Ground limestone refers to mechanically milled limestone, which is commonly used as a supplementary cementitious material or filler in blended cement formulations. The particle size and surface area of ground limestone can be controlled to optimise its interaction with cement hydration products and activator admixtures. Precipitated calcium carbonate is synthetically produced through controlled chemical reactions, typically by carbonating calcium hydroxide, and offers a highly pure and fine-grained form of calcium carbonate with uniform particle morphology. The selection of limestone type may be tailored based on specific requirements, including cement substitution levels, particle size distribution, hydration reactivity, and microstructural effects, to maximise its performance in combination with the activator admixture.

[0279] The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference. Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

[0280] Whilst it will be appreciated that various features of the embodiments may be combined, they may also be used independently of each other.

[0281] It should be noted that the above-mentioned examples illustrate rather than limit the disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.EXAMPLES

[0282] The following examples illustrate embodiments of the invention. Examples in the past tense involve the manufacture and use of activators according to the invention andcement-activator blends that use such activators. Examples in the present tense are hypothetical in nature but illustrative of embodiments within the scope of the invention.

[0283] Throughout the examples, standardised test procedures were followed. Tests are carried out on concrete or mortar, either in the laboratory or in the field, to determine its properties. This information may then be used in a number of ways: to determine whether the concrete complies with the requirements of a specification; to forecast how it will perform in service; to determine the effect of different materials; or simply to determine whether some change is necessary in the mix proportions, e.g. the water content.

[0284] Concrete and mortar is required to have certain properties at two distinct stages: when it is still plastic and when it has hardened. The plastic-state properties determine the ease with which it can be placed and finished, the hardened state properties, how well it will perform in the completed structure. The methodology and relevance of these tests is described below:Sampling

[0285] It is essential that the test results are representative of the concrete being tested. Hence, it is essential that the test sample be representative of the concrete from which it is taken. NZ Standard 3112 sets out procedures for obtaining representative samples from freshly mixed concrete for either consistence (slump) tests or the moulding of specimens for other tests.

[0286] NZS 3104 imposes a number of requirements on the sampling of concrete. Where the sample is being taken to check the quality of the concrete being supplied to a project, it requires that samples be taken after completion of mixing but prior to site handling.Generally, this means that the concrete is sampled at the job site from the delivery truck, although sampling at the concrete plant after mixing is permitted.There are two types of 'sampling' methods:1. Snatch sample. In this case a single sample is taken from one position in the concrete. 2. Representative sample. In this case three or more samples are taken from different positions in the concrete and are then mixed together to form the single sample.

[0287] To ensure that samples are representative of the concrete being delivered to the site, they should be collected in a random manner, i.e. the batches of concrete or delivery units from which the individual samples are taken must be selected randomly, e.g. by using a list of random numbers to select batches. When a consistence or slump test only is to be performed, the test sample should be taken from the delivery or mixer truck immediately after the first 0.1 m3of concrete has been discharged.Plastic-state Properties

[0288] When first mixed, concrete is normally plastic and workable, i.e. able to be placed in formwork and compacted with relative ease. The bulk of concrete delivered to construction sites is workable and cohesive without being fluid or over-wet. Both workability and cohesiveness are important characteristics of concrete in its plastic state. Workability, because it determines the ease with which the concrete can be placed and compacted; cohesiveness, because it determines the tendency of the components in the concrete to segregate one from the other during handling and placing. A concrete may be workable but lack cohesion resulting in segregation, honeycombing and similar defects.

[0289] The workability and cohesiveness of fresh concrete should suit the particular placing conditions and the compaction equipment available. Concrete with 'low' workability will normally require a large compactive effort to achieve maximum density, whilst 'high' workability concrete will be relatively easy to compact.

[0290] Mortar testing is preferred in some instances due to its simplified composition, offering greater consistency and control over variables compared to concrete. It isolates binder properties without the influence of coarse aggregates, facilitating more precise and reproducible results. Additionally, mortar allows for accelerated testing cycles and is ideal for studies focused on cementitious material behaviour.

[0291] Procedures used for the testing of plastic concrete have been standardised by Standards Australia and Standards New Zealand AS 1012 or NZS 3112 Part 1.Test 1 - Workability testing - The Slump Test

[0292] The slump test is fully described in Australian Testing standard AS 1012.3.1 and NZS 3112 Part 1 Section 5. The equipment required to conduct the test comprises a mould (the hollow frustum of a cone 200 mm in diameter at the bottom, 100 at the top, and 300 mm high) made of galvanised sheet metal and fitted with handles and foot-pieces; a steel tamping rod; a rule; and auxiliary equipment such as a scoop, a steel tray and a container in which to collect the sample to be tested. The test is conducted by first obtaining a representative sample of the concrete to be tested. The slump cone is filled with the concrete to be tested in three approximately equal volumes, each layer being rodded 25 times to compact it before the next layer is added. Surplus concrete is struck off the top of the cone which is then removed from the concrete by lifting it slowly and the concrete allowed to subside. The amount by which the top of the cone drops (from the initial 300mm height) is measured and is known as the slump. If, in subsiding, the concrete cone shears or collapses, the test should be repeated using a fresh portion of the sample. If the concrete again shears or collapses, this fact should be recorded as it indicates a lack of cohesiveness in the mixture.Test 2 - Compressive Strength

[0293] Concrete is a naturally strong material in compression, i.e. it can resist high crushing loads. It is relatively weak in tension, i.e. it cracks fairly readily if stretched orbent. It is therefore normally reinforced with steel when it is to be subjected to tension or bending. The compressive strength of concrete is a measure of its ability to resist loads which tend to crush it. When test specimens are fabricated, cured and crushed in accordance with NZS 3112 Part 2, any variation in their compressive strengths should reflect variations in the properties of the concretes, rather than the specimens or the test procedures. It is assessed by measuring the maximum resistance to crushing offered by a standard test specimen. Compression test specimens used for concrete testing were 100mm diameter x 200mm high cylinders. Compression test specimens used for mortar testing were 50x50x50mm cubes. The samples were tested in accordance with NZS3112 part 2.Test 3 - Particle size analysis

[0294] Dry samples were dispersed in water and analysed using a Malvern MasterSizer 3000 according to manufacturer's instructions.Test 4 - Chemical composition analysis

[0295] Dry samples were analysed for chemical composition using Borate fusion / X-ray fluorescence spectrometry according to manufacturer's instructions.Activator development

[0296] In examples 1 and 2 below, concrete activators were tested with natural pozzolans of varying particle size.Example la

[0297] Aim - This experiment tested the effect of different chemical compositions for a given particle size distribution, i.e. similar median particle size Dv50, of a natural pozzolancontaining activator and a plasticiser on compressive strength (at day 1, 3, 7 and 28).

[0298] Methodology - Two sets of concrete mixes were prepared:• Control mix - 20MPa grade concrete.• 2x Activator mix - 20MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3% of cementitious material. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump).The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:

[0299] Samples were prepared according to NZS 3112 Part 1 Section 5. Strength, chemical composition and particle size were tested according to the procedures described in the test protocols 1, 2 and 3 above.

[0300] ResultsSee figures:Figure l.a.i - Comparison of strength over time for activator versus control concrete.Figure l.a.ii - Particle size and volume density of particles for activator gamma.Table 1 showing particle size and % volume under for activator gamma.Figure l.a.iii - Particle size and volume density of particles for activator Omicron.

[0301] Conclusions1. Replacement of standard plasticiser with an activator improved compressive strength at each day of strength setting.2. Activator omicron exhibited increased compressive strength compared to control and gamma activator at each day of strength setting. This indicates that the increase in Silicon Dioxide improves strength.3. Activator omicron exhibited increased compressive strength compared to control and gamma activator at each day of strength setting. This further indicates the increase in overall sum of Silicon Dioxide and Aluminium Oxide improves strength.Based on these experiments, further testing was carried out to test different median particle sizes for a given chemical composition of the activator.Example lb

[0302] Aim - This experiment tested the effect of different particle size medians Dv50 of a natural pozzolan-containing activator, for a given chemical composition and plasticiser level, on strength (at day 1, 3, 7 and 28). The experiment also tested the impact of the pozzolan-containing activator on slump retention.

[0303] Methodology - Two sets of concrete mixes were prepared:• Control mix - 25Mpa grade concrete. Standard aggregates composition. The coarse and fine aggregate amounts are determined according to a standard but proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• 2x Activator mix - 25Mpa grade concrete, as control, with Plasticiser fully replaced by the Activator described below at 3% of total cementitious material by weight and sand volume slightly adjusted to maintain density of the control mix. Water contentis adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Aggregate content was same as control.The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:

[0304] Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0305] ResultsSee figures:Figure l.b.i - Slump loss of concrete over time for control and activator-containing concrete.Figure l.b.ii - Comparison of strength over time for activator versus control concrete showing that the activators produced concrete with higher compressive strength at all time points. Data for day 28 still to come.Figure l.b.iii - Particle size and volume density of particles for activator Tau.Figure l.b.iv - Particle size and volume density of particles for activator 0mega2.Table showing particle size and % volume under for activator Tau.Table showing particle size and % volume under for activator 0mega2.

[0306] Conclusions1. Both activator-containing concretes show significant strength gains as compared to control concrete. This indicates that within the indicated median particle size range Dv(50) < 40 pm, the activator is effective in increasing compressive strength at Dv(50) = 26.3 pm and Dv(50) = 31.1 pm for a given chemical composition.2. Activator Omega2 had increase median particle size, and increase of particle size in each of the defined ranges (which is indicated by decrease % of particles that fall within the specified range). This slightly increased early strength gains (for day 1 and day 3) as compared with the activator tau with a smaller median size. This is of particular interest, because usually strength is increased with decrease in particle size of the pozzolans.3. Both activator-containing concretes shown significant improvement in slump retention as compared to control concrete. This indicates that the activator is effective in increasing slump retention as well as increasing compressive strength.Example 1c

[0307] Aim - This experiment tested the effect of activator containing natural pozzolans on workability (slump) and compressive strength (at day 1,3,7,28) of concrete using Portland cement only as a binder. The aim was to increase the grade of concrete, without increasing cement content. Alternatively, the aim is to test the ability of natural-pozzolans containing activator to reduce cement content in concrete without affecting its workability and strength.

[0308] Methodology - Three sets of concrete mixes were prepared:• Control mix 1 - 25MPa grade concrete. Standard aggregates composition. The coarse and fine aggregate amounts are determined according to a standard but proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• Control mix 2 - 40MPa grade concrete. Standard aggregates composition. The coarse and fine aggregate amounts are determined according to a standard but proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• lx Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3% of cementitious material. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per Control 1.The following concrete compositions were mixed:<<<

[0309] The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0310] ResultsSee figures:Figure l.c.i - Slump loss of concrete over time showing that workability of control 2 and activator retained workability to a similar extent.Figure l.c.ii - Comparison of strength over time for 25MPa concrete, 40MPa concrete, and activator-containing concrete using 25MPa concrete's cement volume with strength at 1, 3, 7 and 28 days post-pour.Figure l.c.iii - Particle size and volume density of particles for activator Pi.Table showing particle size and % volume under for activator Pi.

[0311] Conclusions1. Adding the activator (Pi) at 3% of cementitious material (while removing the plasticiser) to a 25MPa concrete increased the workability and strength of concrete at each age of strength setting.2. Adding the activator at 3% of cementitious material (while removing the plasticiser) increased the grade of concrete from 25MPa to 40MPa. The cement-content in control 1 mix achieved a 25MPa concrete. The activator-containing mix with cement at the same level as control 1 (25MPa) presents similar strength to 40MPa concrete. This means that pozzolanic activator with optimised particle size distribution can increase the grade of concrete by more than 1 grade without increasing cement content of the mix.Specifically, 40MPa concrete performance can be achieved with 29% less cement content, when activator is used at 3% of the resulting cementitious material, without negatively affecting strength and workability of concrete.3. Activator-containing concrete also used substantially less water when compared to both 25MPa and 40MPa control mixes with 33% and 24% less water used respectively.Based on these experiments, further tests were carried out to understand the cement reduction that can be achieved for a given grade of concrete, using the activator and natural pozzolanic SCMs.Example 2a

[0312] Aim - This experiment tested the ability and the extent of a natural pozzolancontaining activator to activate natural pozzolanic SCMs to act like a cement binder. The aim is to replace cement with natural pozzolanic SCMs without detrimental impacts on strength and workability.

[0313] MethodologyTwo sets of concrete mixes were prepared:• Control mix 1 - 25MPa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• 7x Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3-4% of cementitious material. Cement is replaced with natural pozzolans at levels between 0%-40%. Water content isadjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per the control.The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0314] ResultsSee figures:Figure 2.a.i - Slump loss of concrete over time showing good workability for all activatorcontaining concrete mixtures.Figure 2.a.ii - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete at all cement-reduction levels had compressive strength substantially equal to or greater than control at 1, 3, 7 and 28 days post-pour. Figure 2. a . iii - Particle size and volume density of particles for activator Pi.Figure 2.a.iv - Particle size and volume density of particles for activator Tau.Table showing particle size and % volume under for activator Pi.Table showing particle size and % volume under for activator Tau.

[0315] ConclusionsThe following observations were made in relation to cement replacement using activators comprising natural or synthetic pozzolans:1. It is possible to replace a portion of Portland cement with natural pozzolanic supplementary cementitious materials without loss of workability or compressive strength at measured timepoints when the activator is incorporated.2. Activator incorporation enabled cement replacement with natural pozzolans at levels up to and including 40% by weight of cementitious material while maintaining structural performance.3. In certain examples, increased cement replacement levels may be accompanied by increased activator dosage within the ranges described herein. For example, replacement levels up to approximately 35% were achieved using an activator dosage of approximately 3% by weight of cementitious material. Replacement levels of approximately 40% were achieved using an activator dosage of approximately 4% by weight of cementitious material. The activator dosage may be selected within the broader operable range of 0.25-10% depending on the extent of cement substitution.4. In certain examples, increasing activator dosage resulted in increased workability. In certain examples, increasing activator dosage improved slump retention. These rheological improvements may arise from enhanced particle dispersion and packing effects.5. Further cement replacement levels may be achieved by tailoring the chemical composition of the activator. In certain examples, increasing the proportion of silicon dioxide within the activator enhanced compressive strength at approximately 30% cement reduction levels. In certain examples, such compositional adjustment enabled higher strength even at reduced plasticiser levels. Tailoring of activator composition may therefore be used to balance strength development, workability and cement reduction targets.Example 2b

[0316] Aim - This experiment tested the ability and the extent of a natural pozzolancontaining activator to activate synthetic pozzolanic SCMs (Slag) to act like a cement binder. The aim is to replace cement with synthetic SCMs without detrimental impacts on strength and workability.

[0317] MethodologyThree concrete mixes were prepared:• Control mix 1 - 40Mpa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• Control mix 2 - 40Mpa grade concrete, with 50% of cement replaced by synthetic pozzolanic SCMs - Slag. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• lx Activator mix - 40Mpa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3.5% of cementitious material. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per control.The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0318] ResultsTable showing particle size and % volume under for activator Tau.See figures:Figure 2.b.i - Slump loss of activator-containing concrete over time showing significant improvement in workability vs. both controls.Figure 2. b. i i - Comparison of strength over time for activator versus control concrete showing that activator-containing concrete with 50% less cement produced compressive strength greater than controls 1 and 2 at all tested ages - 1, 3, 7 and 28 days post-pour. Figure 2. b. iii - Particle size and volume density of particles for activator Tau.

[0319] Conclusions1. Concrete samples made from natural pozzolan-containing activator maintained workability and strength when 50% of the cement in a standard mix was replaced with synthetic pozzolanic SCMs.2. Strength and workability were significantly higher for the Activator enhanced mix vs both control mixes which respectively comprised:a. no cement reduction; andb. similar cement reduction.3. Activator-containing concrete enables the replacement of cement with synthetic pozzolans at over 50% replacement. This indicates that the pozzolanic activators of theinvention enhance the binding activity of synthetic pozzolans at a higher efficiency than the enhancement of binding activity of natural pozzolans.4. At higher cement replacement levels, higher dosage of activator can be used, for example 3.5% for 50% replacement levels.5. With increase of the activator dosage, the workability and slump retention further increase.6. Based on the data, it is expected that higher cement replacement percentage is possible e.g. 60% or 70% while maintaining equal or greater strength compared to cementcontaining control samples. This is predictable based on the significant strength surplus was observed at each age of strength setting.7. The natural-pozzolans containing activator can activate both natural and synthetic pozzolans to become an effective binder similar or better in properties to cement.Example 2c

[0320] Aim - This experiment tested the ability and the extent of a natural pozzolancontaining activator to activate natural pozzolanic SCMs to act like a cement binder.Two sets of concrete mixes were prepared:• Control mix 1 - 35MPa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• KNP mix - 35MPa grade concrete, as control, but with an added mid-range plasticiser and 20% of cement replaced by KNP activated natural pozzolans. Water content is adjusted to achieve target slump on mixing of 60mm (+-20mm permissible tolerance on slump). Sand and aggregates as per the control.• Control mix 2 - 25MPa grade concrete. The coarse and fine aggregate are prepared according to a proprietary composition by a third party. The amount of these components can vary and a skilled person in the art would be able to readily determine suitable components and mass required.• Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3-4% of cementitious material. 20% cement is replaced with natural pozzolans. Water content is adjusted to achieve target slump on mixing of 180mm (+-40mm permissible tolerance on slump). Sand and aggregates as per the control.The following concrete compositions were mixed:< < <The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:Samples were obtained from freshly mixed concrete, in accordance with NZS 3112, using Snatch Sample method, and slump loss was measured over time in 30 mins increments, according to NZS 3112 Part 1 Section 5. Slump (workability), strength and particle size were tested according to the procedures described in Test 1, 2 and 3 above.

[0321] ResultsTable showing particle size and % volume under for activator Pi.Figure 3 - Comparison of strength over time for KNP activated natural pozzolans vs control and Activator activated pozzolans vs. control, both at 20% cement replacement levels. Figure 4 - Particle size and volume density of particles for activator Pi.

[0322] Conclusions1. KNP Activated natural pozzolans achieved slightly lower strength than control concrete at 20% cement replacement levels.2. Natural pozzolans at 20% cement replacement levels activated by the activator, achieved at least 25% increase in strength at each tested age of strength setting as compared to control.3. This indicates that activator is more effective at activating the natural pozzolans in achieving compressive strength that the KNP patented technology to activate natural pozzolans.4. Further cement replacement levels with natural pozzolans are possible of up to 40%, with the activator, as presented in example 2a, and for 50% and above for industrial pozzolans.Example 3 - carbon emission reduction through use of activators of the invention

[0323] Activators of the invention provide the ability to reduce the carbon emissions associated with preparation of a volume of concrete. This example illustrates the carbon emission reductions associated with the concrete mix ratios described in example 2c when applied to a larger scale concrete preparation project - two concrete mixes comprising activator of the invention versus a control mix.Volume of concrete to be used in the project - 100m3Grade of concrete - 25 MPaThree concrete mixes prepared:• Control mix - 25MPa grade concrete.• 2x Activator mix - 25MPa grade concrete, as control, but with Plasticiser fully replaced by the Activator described below at 3% of cementitious material and 30% and 40% cement replaced by NZ natural pozzolan (pumice).The following concrete compositions were mixed:<<<The Activator concrete contained an activator of the invention described herein. The activator had the following chemical composition:

[0324] ResultsThe embodied carbon emissions of each mix were estimated using Neocrete eCalculator, a tool developed by an independent LCA assessor - Edge Environment to estimate the embodied carbon emissions per m3of concrete in NZ, using average NZ data for embodied carbon for each of the materials used.Life cycle assessment (LCA) per m3of the ready mix concrete in New Zealand

[0325] ConclusionsConcrete containing activator with cement replacement with NZ natural pozzolans at 30% and 40% has less embodied carbon than control, by 21% and 28%, respectively.Example 4 - Analysis of permeability of activator-containing concreteAim

[0326] This experiment tested the special durability characteristics of concrete with significant cement reduction levels, partly replacement by natural pozzolans and containing the activator.

[0327] MethodologyConcrete with cement replaced by an activator of the invention was analysed for special durability characteristics:• water permeability BS EN 12390-8:2019 "Depth of penetration of water under pressure"• water absorption AS 1012.12• water sorptivity ASTM C1585• Rapid chloride penetrationSample cores of concrete were prepared and allowed to set for 28 - 56 days.

[0328] Results0329] ConclusionsConcrete prepared using an activator of the invention with 30% reduced cement in the mix, and provided• enhanced resistance to water penetration over and above control concrete with no cement reduction• enhanced resistance to chloride penetration over and above control concrete with no cement reduction• reduced volume of voids and immersed and boiled absorption• enhanced sorptivity, i.e. reduced initial and secondary rate of absorptionThis demonstrates the ability of the concrete containing the activator to have significantly enhanced durability characteristics at significantly lower cement levels, which is partly explained by the tighter microstructure of concrete as a result of optimal chemical and physical properties of the activator.Example 5

[0330] Aim - This experiment tested various activators of the invention to exemplify their ability to increase compressive strength in mortar at different time points while maintaining cement content compared to a control with no activator and substantially the same mortar mix design.

[0331] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Three different activators were used - XI, X2 and X3. The mixes contained 25% less cement than standard concrete mixtures demand and this was replaced with natural pozzolan (NZ pumice).The activators had the following particle sizes and chemical compositions:For Activator XI the particle size distribution is shown in Figure 5A and the table below:For Activator X2 the particle size distribution is shown in Figure 5B and the table below:For Activator X3 the particle size distribution is shown in Figure 5C and the table below:Activator Particle characteristics:<<<

[0332] Predictive Method for Estimating 28-Day Compressive StrengthTo estimate the 28-day compressive strength of concrete samples where direct measurements were unavailable, a predictive modeling approach was employed. This method leverages the strength development trends observed in other samples to provide accurate predictions.Data Input - The available compressive strength data for the concrete samples was recorded at 1, 3, and 7 days. The 28-day strength was missing for three samples denoted as X2, X4, and X5.Model Selection - A logarithmic growth model was chosen to represent the relationship between compressive strength and time. The chosen model reflects the common understanding that the rate of strength gain in concrete decreases over time. The equation used for the prediction was as follows:Strength=axln(day+b)+c where:• Strength is the compressive strength of the concrete at a given day,• day is the time in days,• a, b, and c are parameters to be determined from the data.Curve Fitting - For each of the samples, the above model was fitted to the known data points (1-day, 3-day, and 7-day strengths). The fitting process was carried out using nonlinear regression to optimize the parameters a, b, and c such that the model best matched the observed data.Prediction - Once the model parameters were determined, the model was used to extrapolate the compressive strength at 28 days. These predicted values were derived based on the logarithmic trend of strength gain observed in the earlier days and are consistent with the expected behaviour of concrete strength development over time.

[0333] ResultsConcrete properties are provided in Figure 5D and in the table below.*28-day data is predicted based on the model outlined and in accordance with samples with substantially identical 1,3 and 7 day results.

[0334] ConclusionsAll activators of the invention provide increased compressive strength at days 3, 7 and 28 compared to control while maintaining workability (slump).Activator X2 exhibits significantly higher early strength (days 1, 3 and 7) compared to XI and X3.Example 6

[0335] Aim - This experiment tested various activators of the invention to exemplify their ability to increase compressive strength in mortar at different time points while maintaining cement content compared to a control with no activator and substantially the same mortar mix design.

[0336] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Two different activators were used - X2 and X4.The activators had the following particle sizes and chemical compositions:For Activator X2 the particle size distribution is shown in Figure 5B and the table in Example 5For Activator X4 the particle size distribution is shown in Figure 6A and the table below:Activator Particle characteristics:<<<Where 28 day data was not yet available, the predictive model in example 5 was used to predict it.

[0337] ResultsConcrete properties are provided in Figure 6B and in the table below.*28-day data is predicted based on the predictive model outlined for example 5.

[0338] Conclusions - All activators of the invention provide increased compressive strength at days 3, 7 and 28 compared to control while maintaining workability (slump). Example 7

[0339] Aim - This experiment tested activators of the invention to exemplify their ability to maintain or increase compressive strength in mortar at different time points with reduced cement.

[0340] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Activator X4 was used which had the particle size characteristics and chemical composition as described in Example 6.

[0341] ResultsConcrete properties are provided in Figure 7 and in the table below.

[0342] ConclusionsThe activator of the invention increased compressive strength at days 1, 3, 7 and 28 compared to control while maintaining workability (slump). Cement reduction of 10% was achieved while maintaining increased compressive strength compared to control.Example 8

[0343] Aim - This experiment tested activators of the invention to exemplify their ability to maintain or increase compressive strength in mortar containing fly ash at different time points with reduced cement.

[0344] Methodology - 2L of mortar was prepared for each mix according to the following procedure:1. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec. 2. Sand added over 30 seconds while mixing at slow speed.3. High speed mixing at 30 seconds then let mortar stand for 1.5 min.4. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Activator X2 was used. The X2 activator had the particle size characteristics and chemical composition as described in Example 5.

[0345] Results - Concrete properties are provided in Figure 8 and in the table below.* - These values were predicted based on the model described in relation to example 5.

[0346] Conclusions - The experiment using activator X2 exhibits higher strength in the 45% substitution versus the 12% fly ash sample and control due to the higher amount of pozzolanic material able to be activated by the activator. For the high (60%) fly ashsubstitution, there is a higher water demand to maintain workability. At this high substitution, the excess water required results in a reduction in compressive strength as compared to the lower substation (but is still higher than control). Without activator, the high water demand prevents the fly ash from being usable as a substitute. The activatorcontaining concrete enables the use of high substitution levels of fly ash without negatively affecting the workability.The activator of the invention maintained or increased compressive strength at days 1, 3, 7 and 28 compared to control while maintaining workability (slump). Cement reduction of 30% was achieved with addition of varying amounts of fly ash at activator percentage between 2.3 and 3.7.Example 9 - Surface Activation via electrolysis

[0347] Aim - This experiment tests the ability and extent of a pozzolan-containing activator, which is subjected to an electrical charge, to activate pozzolanic supplementary cementitious materials (SCMs) to function as a cement binder. The objective is to replace cement with SCMs without detrimental impacts on strength and workability.

[0348] Methodology - Six concrete mixes are prepared:1. Control mix 1: 25 MPa grade concrete. The coarse and fine aggregates are prepared according to a proprietary composition by a third party. The amount of these components do not vary across the three treatments proposed herein, but can vary when used in situ for concrete production. A skilled person in the art would be able to readily determine suitable aggregate components and mass required. A powdered polycarboxylate plasticiser is used.2. Control mix 2: 25 MPa grade concrete, with 30% of cement replaced by synthetic pozzolanic SCMs (Slag). The coarse and fine aggregates are provided in the same proportions as in mix 1. A powdered polycarboxylate plasticiser is used.3. Activator mix 3 (XO): 25 MPa grade concrete, with 30% of cement replaced by synthetic pozzolanic SCMs (Slag) and a standard (non-electro-activated) activator added at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1. A powdered polycarboxylate plasticiser is used.4. Electro-activated mix 4 (XVI): 25 MPa grade concrete, with 30% of cement replaced by natural pozzolans (NZ pumice) with electro-activated activator described below at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1.5. Electro-activated mix 5 (XV2): 25 MPa grade concrete, with 30% of cement replaced by synthetic pozzolanic SCMs (Slag) with electro-activated activator described below at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1.6. Electro-activated mix 6 (XV3): 25 MPa grade concrete, with 30% of cement replaced by fly ash with electro-activated activator described below at 3% of cementitious material. The coarse and fine aggregates are provided in the same proportions as in mix 1.Water content for each mix is adjusted to achieve a target slump on mixing of 180 mm (±40 mm permissible tolerance on slump). Sand and aggregates as per control.The following concrete compositions are mixed:The electro-activated mix contains an activator subject to an electrica charge before formulation with other concrete components. The activator is formulated to have the chemical composition provided for X2 in example 5 above.

[0349] Electro-Activation Process:A non-conductive container is used to hold the powdered activator. The container is equipped with two electrodes made of an inert material (e.g., graphite or platinum) to prevent any unwanted reactions with the admixture. A direct current (DC) power supply with adjustable voltage and current settings is connected to the electrodes. The powdered activator is evenly spread within the container, ensuring good contact with the electrodes. The depth of the powder should allow for efficient electro-activation while avoiding excessive resistance. The power supply is set to a low voltage (12V) and current (2A). The current is passed through the powdered admixture for a duration of 30 minutes to one hour. This timeframe is sufficient to induce electrical activation. During electro-activation, thepowder is gently stirred using a non-conductive stirrer at regular intervals (every 5-10 minutes) to ensure uniform exposure to the electric field. After the activation period, the electrical current is turned off, and the powder is allowed to cool and settle. This step ensures that the entire batch of the activator is uniformly charged and ready for use in concrete mixes.

[0350] ResultsResults show that control mix 2 has lower strength compared to the control 1. In accordance with earlier embodiments of the invention, activator XO exhibits equivalent slump with improved compressive strength versus control 1 and control 2. The electroactivated XVI, XV2 and XV3 concrete shows increased strength at time points 1,3,7 compared to the activator XO due to the enhanced surface activation leading to higher reactivity with pozzolan replacements.

[0351] Conclusions

[0352] Electro-activated activator provides increased early strength due to the enhanced surface activation of the activator particles and increased binding activity with pozzolan SCMs (e.g. synthetic or natural pozzolans).

[0353] At higher cement replacement levels, the dosage of activator may be increased within the operable ranges described herein. For example, cement replacement levels of approximately 40% may be achieved using an activator dosage of approximately 3.5% by weight of cementitious material, and replacement levels of approximately 50% may be achieved using an activator dosage of approximately 4% by weight of cementitious material. The relationship between cement substitution level and activator dosage may be selected according to the type and proportion of supplementary cementitious materials and the desired mechanical performance of the resulting concrete composition.

[0354] Based on the data, it is expected that a higher cement replacement percentage is possible (e.g., 60% or 70%) while maintaining equal or greater strength compared to cement-containing control samples. This is predictable based on the significant strength surplus observed at each age of strength setting.

[0355] The electro-activated activator can activate both natural and synthetic pozzolans to become an effective binder similar to or better in properties than cement.

[0356] This example demonstrates the enhanced performance of concrete when using an electro-activated activator, highlighting the potential benefits of applying an electrical charge to the activator prior to inclusion in the concrete mix.Example 10

[0357] Aim - This experiment tested activators of the invention to exemplify their ability to maintain or increase compressive strength in mortar at different time points with reduced cement.

[0358] Methodology - 2L of mortar was prepared for each mix according to the following procedure:5. Cement added to water in a mixing vessel and mixed at a slow speed for 30 sec.6. Sand added over 30 seconds while mixing at slow speed.7. High speed mixing at 30 seconds then let mortar stand for 1.5 min.8. Mix at high speed for 1 min.Mortar was prepared according to the following composition:Activator X2 was used which had the particle size characteristics and chemical composition as described in Example 5.

[0359] ResultsConcrete properties are provided in Figure 10 and in the table below.Conclusions25% and 50% reduction in cement and replacement with natural pozzolan significantly reduced compressive strength at all time points.When activator was added at 3% of cementitious material, compressive strength for both 25% and 50% pozzolan substituted mixes increased significantly compared to the respective mixes not containing activator X2.Example 11Aim - This experiment tested activators of the invention to exemplify their ability to increase the reactivity of filler materials such as limestone when used as a cement replacement.Grade of concrete - 25 MPaFour concrete mixes prepared:• Control (no activator)• Cement replacement (30%) with Pozzl (15%) and Limestone (15%)• Cement replacement (30%) with Pozzl (10%) and Limestone (20%)

[0360] Methodology - as described example 1Activator Tau was used which had the particle size characteristics and chemical composition as described in examples lb, 2a, 2b and 3.Results

[0361] Concrete properties are provided in Figure 11 and in the table below.Conclusions

[0362] Both cement replacement formulations outperformed the control at all ages, demonstrating the effectiveness of the activator in enhancing the reactivity of pozzolan SCMs and limestone.

[0363] Early strength (Day 1) was significantly higher in both activated mixes compared to the control (9 MPa), with 15% Pozzl + 15% limestone reaching 14 MPa and 10% Pozzl + 20% limestone reaching 12 MPa, indicating improved early hydration. At Day 3, the Pozzl + limestone mixes were 10 MPa or more stronger than the control (36 MPa vs. 26 MPa and 30 MPa vs. 26 MPa), suggesting that the activator promotes faster strength development. By Day 28, both activated mixes exceeded the control by more than 20 MPa, with the 15% Pozzl + 15% limestone mix reaching 66 MPa, while the 10% Pozzl + 20% limestone mix achieved 58 MPa, confirming the long-term benefits of combining limestone and Pozzl. At Day 56, strength improvements continued, with the 75 MPa result for the 15% Pozzl + 15% limestone mix being 22 MPa higher than the control, and the 10% Pozzl + 20% limestone mix reaching 66 MPa, showing sustained performance benefits.Comparative Performance of Pozzl-Limestone Blends

[0364] The 15% Pozzl + 15% limestone mix consistently achieved the highest strength at all ages, making it the most effective formulation for both early and long-term performance. Increasing the limestone content to 20% (with 10% Pozzl) still resulted in significant strength gains over the control, though slightly lower than the 15% Pozzl + 15% limestone mix. The early strength difference between the two Pozzl-limestone mixes is small (2 MPa at Day 1 and 6 MPa at Day 3), but the gap widens at later ages, indicating that the optimal pozzolan-limestone balance (15% Pozzl + 15% limestone) maximises long-term strength development.Key Findings

[0365] Activator-enhanced Pozzl-limestone blends significantly outperform the control at all ages, confirming that the activator effectively enhances reactivity. Pozzl and limestone formulations show superior strength compared to the control, even at a 30% cement reduction. 15% Pozzl + 15% limestone is the optimal mix, providing the highest strength across all time points, particularly at later ages. Increasing limestone to 20% (reducing Pozzl to 10%) still results in high performance, though slightly lower than the 15%-15% mix, suggesting that a balance between pozzolanic and carbonate reactivity is important for maximising strength. The activator effectively promotes both early and long-term strength, making these formulations viable for high-performance, low-cement concrete applications.Example 12 - 30% Limestone Replacement

[0366] This experiment tested the effect of 30% limestone as a cement replacement in concrete. The performance of a limestone-containing mix incorporating an activator of the invention was compared against a limestone-containing mix incorporating a conventional water reducer and a 100% cement control.Methodology

[0367] Three concrete mixes were prepared:Control 1 - 100% cementControl 2 - 70% cement + 30% limestone + water reducerTreated - 70% cement + 30% limestone + 3% activator (K4e)All mixes were designed to achieve substantially the same w / b ratio for the limestonecontaining compositions (0.51). Aggregates were maintained constant across treatments. Super plasticiser was Rockbond 6.16N Hyper-Plasticiser in this and subsequent examples including a plasticiser.

[0368] Activators K4e, A+, were analysed for chemical composition and particle size data. A+ is reported in this example for convenience but are applicable to other examples.Mix Design

[0369] Each mix was prepared in triplicate. Fresh properties were measured immediately after mixing. Compressive strength was determined at 1, 3, 7 and 28 days.ResultsParticle size data for activator K4e, A+ is as follows and shown in Figure 17:<<<Activators K4e and A+ exhibit substantially identical particle size distributions (shown in Figure 17), but differ in chemical composition as reflected in the oxide analysis values above.

[0370] The treated mix exhibited workability comparable to the limestone control and acceptable yield. Compressive strength results are shown below and in Figure 12.

[0371] Statistical Analysis (Day 28) - A one-way ANOVA test for 28-day compressive strength produced a p-value < 0.05, indicating statistically significant differences among the three groups. Post hoc Tukey HSD testing confirmed that both limestone-containing mixes were significantly lower in strength than the 100% cement control. The difference between the limestone + activator mix and the limestone + water reducer mix was not statistically significant at Day 28.Conclusions

[0372] Replacement of 30% cement with limestone resulted in a substantial reduction in compressive strength at all ages when compared to the 100% cement control. The addition of 3% activator to the limestone-containing mix significantly increased compressive strength at all early ages relative to the limestone + water reducer control. Strength increases relative to the limestone control were approximately: Day 1: +39%, Day 3:+38%, Day 7: +30%, Day 28: +8%. Despite these improvements, both limestonecontaining mixes remained lower in strength than the 100% cement control at all ages. The treated mix demonstrated comparable workability and yield relative to controls at the same w / b ratio (0.51), confirming that the strength improvements were not attributable to water reduction. These results demonstrate that the activator enhances early-stage strength development in limestone-containing cement systems, supporting its suitability for applications requiring improved early strength performance in reduced-cement concrete compositions.Example 13 - 20% Limestone + 10% Fly Ash Replacement

[0373] This experiment tested the effect of combined 20% limestone and 10% fly ash as cement replacement in concrete. The performance of a blended limestone-fly ash mix incorporating an activator of the invention was compared against an equivalent mix incorporating a conventional water reducer and a 100% cement control. Fresh and hardened properties were assessed, including workability, air content, yield, and compressive strength development.

[0374] Three concrete mixes were prepared:Control 1 - 100% cementControl 2 - 70% cement + 20% limestone + 10% fly ash + water reducerTreated - 70% cement + 20% limestone + 10% fly ash + 3% activator (K4e) Aggregates were maintained constant across treatments.Mix DesignEach mix was prepared in triplicate. Fresh properties were measured immediately after mixing. Compressive strength was determined at 1, 3, 7 and 28 days.Results

[0375] The treated mix exhibited workability comparable to the limestone-fly ash control and greater than the 100% cement control. Yield values were similar across all mixes. Air content increased in the activator-containing mix.Compressive Strength (Average of 3 Replicates)

[0376] A one-way ANOVA test for 28-day compressive strength produced a p-value < 0.05, indicating statistically significant differences among the three group means. Post hoc Tukey HSD testing confirmed that both limestone-fly ash mixes were significantly lower in strength than the 100% cement control. The difference between the limestone-fly ash + water reducer mix and the limestone-fly ash + activator mix was not statistically significant at Day 28.Conclusions

[0377] Replacement of 30% cement with a blended system comprising 20% limestone and 10% fly ash resulted in a reduction in compressive strength at all ages relative to the 100% cement control.

[0378] The addition of 3% activator to the limestone-fly ash mix increased compressive strength at all ages relative to the limestone-fly ash + water reducer control. Strengthincreases relative to the limestone-fly ash control were approximately: Day 1: +47%, Day 3: +33%, Day 7: +20%, Day 28: +15%. The treated mix demonstrated comparable or improved workability relative to controls at the same w / b ratio (0.50), confirming that strength improvements were not attributable to water reduction. These results demonstrate that the activator enhances early-stage strength development in blended cement systems containing limestone and fly ash, supporting its suitability for use in reduced-clinker concrete formulations requiring improved early strength performance.Example 14 - Evaluation of activator admixtures in 100% Cement System

[0379] This experiment investigated the effect of the activator admixture in a 100% cement concrete system under target spread (TS) conditions. Mixes with and without the activator were adjusted to achieve substantially identical slump (180-200 mm at 0 minutes). The objective was to assess the impact of the activator on water demand, fresh properties, and compressive strength development.Methodology

[0380] Mixes were designed to achieve comparable initial workability (target slump 180-200 mm at 0 minutes). Water content was adjusted during mixing to achieve the desired spread without the addition of other admixtures. All mixes containing activator incorporated 3% activator by weight of total cementitious material. Moisture content of sand was measured prior to each day of trials and mix designs were adjusted accordingly. Trial mix proportions were scaled from a 30 L laboratory mix based on a 150 L water design.

[0381] All fresh concrete testing was conducted in accordance with NZS 3112.1, including slump (0 minutes), density, air content, and yield. Compressive strength testing was conducted in accordance with NZS 3112.2 at 1, 3, 7, 14, and 28 days. Activator A+ was used.Mix DesignResultsCompressive strength results are shown in Figure 13 and the table below:Conclusions

[0382] The treated mix comprising 100% cement and 3% activator demonstrates a substantial increase in compressive strength at all measured ages relative to the 100% cement control. Relative strength increases were approximately: Day 1: +98%, Day 3: +69%, Day 7: +63%, Day 14: +57%, Day 28: +50%. The treated mix achieved the target slump (200 mm) with significantly reduced water demand compared to the control (154 L vs 210 L), resulting in a substantially lower w / b ratio (0.44 vs 0.60). Yield values were substantially identical, and air content remained within acceptable limits.

[0383] These findings demonstrate that the activator enables improved material efficiency in cementitious systems by reducing water demand while increasing both early-age and later-age strength, supporting its suitability for high-performance concrete applications requiring enhanced strength development and optimised rheology.Example 15 - 30% Limestone Replacement

[0384] This experiment investigated the effect of 30% limestone as a cement replacement under target spread (TS) conditions. Mixes with and without activator were adjusted to achieve substantially identical initial slump (180-200 mm at 0 minutes) by altering water content. Fresh and hardened properties were assessed, including workability, air content, yield, and compressive strength development.Methodology

[0385] Three mixes were prepared:• Control 1 - 100% cement• Control 2 - 70% cement + 30% limestone• Treated - 70% cement + 30% limestone + 3% activator (A+)All activator-containing mixes incorporated 3% activator by weight of total cementitious material. Water content was adjusted during mixing to achieve the target slump (180-200 mm at 0 minutes), without the use of additional water-reducing admixtures. Moisture corrections were applied to aggregates prior to batching. Fresh concrete testing was conducted in accordance with NZS 3112.1 (slump, density, air, yield). Compressive strength testing was conducted in accordance with NZS 3112.2 at 1, 3, 7, 14, and 28 days.Results

[0386] Compressive strength results are shown below and in Figure 14.

[0387] Replacement of 30% cement with limestone at equivalent water content (w / b = 0.60) resulted in a substantial reduction in compressive strength at all ages relative to the 100% cement control. The limestone control exhibited reductions of approximately :Day 1: -53%, Day 3: -41%, Day 7: -42%, Day 14: -44%, Day 28: -42%. Incorporation of 3% activator into the 30% limestone system significantly increased compressive strength relative to the limestone control at all ages. Strength improvements relative to the limestone control were approximately: Day 1: +43%, Day 3: +66%, Day 7: +71%, Day 14: +76%, Day 28: +57%. When compared to the 100% cement control, the treated mix demonstrated: Day 1: -32%, Day 3: -2%, Day 7: equivalent strength, Day 14: -2%, Day 28: -9%. Notably, by Day 7 the activator-containing limestone mix achieved substantially equivalent strength to the 100% cement control, despite a 30% reduction in cement content.

[0388] The treated mix achieved the target spread using substantially lower water content (153 L) compared to both control mixes (210 L), resulting in a reduced w / b ratio of 0.44 compared to 0.60 for the controls. Yield values were similar across all mixes. Air content increased modestly in the activator-containing mix (1.9%) but remained within acceptable limits.

[0389] The treated composition exhibits strength recovery and near-parity with full cement at intermediate ages which indicates that the activator both reduces water demand and enhances binder reactivity in limestone-containing systems. These results confirm thatchemical activation of a 30% limestone replacement system significantly bridges the performance gap between blended and pure cement systems under practical workability conditions, enabling high-workability, low-water concrete compositions while maintaining acceptable structural performance despite substantial clinker reduction.Example 16 - 20% Limestone + 10% Fly Ash Replacement

[0390] This experiment investigated the effect of combined 20% limestone and 10% fly ash as cement replacement. Mixes with and without activator were adjusted to achieve substantially identical initial slump (180-200 mm at 0 minutes) by altering water content. Fresh and hardened properties were assessed, including workability, air content, yield, and compressive strength developmentMethodology

[0391] Three mixes were prepared:• Control 1 - 100% cement• Control 2 - 70% cement + 20% limestone + 10% fly ash• Treated - 70% cement + 20% limestone + 10% fly ash + 3% activator (A+) All activator-containing mixes incorporated 3% activator by weight of total cementitious material. Water content was adjusted during mixing to achieve the target slump (180-200 mm at 0 minutes), without the use of additional superplasticisers or water-reducing admixtures. Aggregate moisture corrections were applied prior to batching.Mix designResultsCompressive strength results shown below and in figure 15.Conclusions

[0392] Replacement of 30% cement with a blended system comprising 20% limestone and 10% fly ash resulted in reduced compressive strength at all ages relative to the 100% cement control, with strength reductions of approximately 46% at Day 1, 41% at Day 3, 34% at Day 7, 36% at Day 14, and 37% at Day 28. Incorporation of 3% activator into the limestone-fly ash system resulted in substantial strength recovery and subsequent enhancement relative to both controls, with increases relative to the limestone-fly ash control of approximately 81% at Day 1, 89% at Day 3, 73% at Day 7, 68% at Day 14, and 81% at Day 28. When compared to the 100% cement control, the treated mix demonstrated a 2% decrease at Day 1 (substantially equivalent strength), followed by increases of approximately 12% at Day 3, 14% at Day 7, 8% at Day 14, and 14% at Day 28, indicating that the activator-containing limestone-fly ash system not only recovered the strength deficit associated with cement reduction but exceeded the full cement control from Day 3 onward. The observed strength enhancement confirms that chemical activation enables a ternary limestone-fly ash system to deliver equal or superior structural performance under practical workability conditions despite a 30% reduction in cement content.Example 17 - 20% Limestone + 10% Pl Replacement

[0393] This experiment investigated the effect of combined 20% limestone and 10% natural pozzolan Pl (NZ pumicite) as cement replacement. Mixes with and without activator were adjusted to achieve substantially identical initial slump (180-200 mm at 0 minutes) by altering water content.Methodology

[0394] Three mixes were prepared:Control 1 - 100% cementControl 2 - 70% cement + 20% limestone + 10% PlTreated - 70% cement + 20% limestone + 10% Pl + 3% activator (A+)All activator-containing mixes incorporated 3% activator by weight of total cementitious material. Water content was adjusted during mixing to achieve the target slump (180-200 mm at 0 minutes), without the use of additional water-reducing admixtures. Aggregate moisture corrections were applied prior to batching.Mix designResults

[0395] Compressive strength results are shown in the table below and in figure 16Conclusions

[0396] Replacement of 30% cement with a blended system comprising 20% limestone and 10% Pl resulted in reduced compressive strength at all ages relative to the 100% cement control, with strength reductions of approximately 50% at Day 1, 43% at Day 3, 36% at Day 7, 42% at Day 14, and 39% at Day 28. Incorporation of 3% activator into the limestone-Pl system resulted in substantial strength recovery relative to the limestone-Pl control, with increases of approximately 73% at Day 1, 67% at Day 3, 58% at Day 7, 63% at Day 14, and 55% at Day 28. When compared to the 100% cement control, the treated mix demonstrated a 13% decrease at Day 1, a 4% decrease at Day 3, a 1% increase at Day 7 (substantially equivalent performance), and 5% decreases at both Day 14 and Day 28. The strength recovery observed in the activator-containing system reflects enhanced binder reactivity relative to the limestone-Pl control. These results confirm that the activator enhances strength development in limestone-Pl blended systems relative to equivalent non-activated blends, while maintaining workability.Clauses

[0397] The following numbered clauses define further optional embodiments of the invention described herein. The clauses are provided for the purpose of illustratingcombinations of features disclosed in the specification and are not intended to limit the scope of the invention as defined in the claims.

[0398] Features described in relation to one clause may be combined with features described in any other clause, unless the context clearly indicates otherwise. Any feature described in relation to an activator admixture may also apply, where appropriate, to a concrete composition comprising the activator, to a method of producing the activator, to a method of producing a limestone concrete composition, or to the use of the activator.Clause 1. An activator admixture for producing limestone-containing concrete, the activator comprising a pozzolan component, wherein the pozzolan component comprises a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes or different chemical compositions.Clause 2. The activator of Clause 1, further comprising a powdered plasticiser component mixed with the pozzolan component.Clause 3. The activator of Clause 1 or Clause 2, wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.Clause 4. The activator of any preceding Clause, wherein the Dv50 of the activator is less than 50 pm.Clause 5. The activator of any preceding Clause, wherein the first pozzolan portion comprises an intermediate median particle size in a range of 0.5-1.5 pm and the second pozzolan portion comprises a coarse median particle size in a range of 10-80 pm.Clause 6. The activator of any preceding Clause, wherein the pozzolan component exhibits a first volume density peak within 0.5 pm to 1.5 pm and a second volume density peak within 10 pm to 80 pm.Clause 7. The activator of any preceding Clause, wherein the particle size distribution is defined by:(a) 15-55% of particles are less than 15 pm;(b) 50-80% of particles are less than 40 pm; and(c) 70-100% of particles are less than 90 pm.Clause 8. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least 2x the Dv50 of the first pozzolan portion.Clause 9. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least 4x the Dv50 of the first pozzolan portion.Clause 10. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least 6x the Dv50 of the first pozzolan portion.Clause 11. The activator of any preceding Clause, wherein the Dv50 of the second pozzolan portion is at least lOx the Dv50 of the first pozzolan portion.Clause 12. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 10 pm.Clause 13. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 20 pm.Clause 14. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 30 pm.Clause 15. The activator of any preceding Clause, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 50 pm.Clause 16. The activator of any preceding Clause, wherein the first and second pozzolan portions occupy distinct particle size domains and form separate peaks within a bi-modal or multi-modal particle size distribution of the activator.Clause 17. The activator of any preceding Clause, wherein particles of the first pozzolan portion occupy interstitial spaces between particles of the second pozzolan portion.Clause 18. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in silicon dioxide content by at least 5% w / w.Clause 19. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in silicon dioxide content by at least 10% w / w.Clause 20. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in silicon dioxide content by at least 15% w / w.Clause 21. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in aluminium oxide content by at least 5% w / w.Clause 22. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in aluminium oxide content by at least 10% w / w.Clause 23. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in aluminium oxide content by at least 15% w / w.Clause 24. The activator of any preceding Clause, wherein the first and second pozzolan portions differ in one or both of silicon dioxide and aluminium oxide content.Clause 25. The activator of any preceding Clause, wherein the activator comprises an electrostatic charge.Clause 26. The activator of any preceding Clause, wherein the activator is formulated for addition at between 0.25-10% by weight of cementitious material in a limestone-containing concrete composition.Clause 27. The activator of any preceding Clause, wherein the activator is formulated for addition at between 0.5-8% by weight of cementitious material in a limestone-containing concrete composition.Clause 28. The activator of any preceding Clause, wherein the activator is formulated for addition at between 1-4% by weight of cementitious material in a limestone-containing concrete composition.Clause 29. A method of producing an activator composition for use in limestone-containing concrete, the method comprising:(a) obtaining a first pozzolan portion having a first chemical composition and / or a first median particle size and a second pozzolan portion having a second chemical composition and / or a second median particle size;(b) combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component; and(c) mixing the pozzolan component with a plasticiser to produce the activator composition, wherein the pozzolan component comprises 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.Clause 30. The method of Clause 29, wherein the activator comprises an electrostatic charge applied by electrostatic spraying, triboelectric charging, corona discharge, electrostatic fluidisation, or mechanical mixing-induced friction.Clause 31. The method of Clause 29 or 30, wherein the activator comprises an activator of any of clauses 1 to 18.

Claims

What we claim is:

1. A concrete composition comprising an activator admixture, cementitious material, and limestone, wherein the activator admixture comprises a pozzolan component, the pozzolan component comprising a first pozzolan portion and at least a second pozzolan portion, wherein the first and second pozzolan portions comprise different median particle sizes and different chemical compositions.

2. The concrete composition of claim 1, wherein the limestone comprises up to 30% by weight of the cementitious material.

3. The concrete composition of claim 2, wherein the limestone is selected from 5-15% w / w, 15-25% w / w, or 25-30% w / w of the cementitious material.

4. The concrete composition of any of the preceding claims, wherein the limestone is selected from natural limestone, processed limestone, ground limestone, or precipitated calcium carbonate.

5. The concrete composition of any of the preceding claims, wherein the limestone comprises at least 90% calcium carbonate (CaCOs).

6. The concrete composition of any of the preceding claims, wherein the limestone comprises a median particle size in a range of l-150pm.

7. The concrete composition of any of the preceding claims, wherein the activator pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% w / w aluminium oxide.

8. The concrete composition of any of the preceding claims, wherein the activator admixture comprises an electrostatic charge.

9. The concrete composition of any of the preceding claims, wherein the activator first pozzolan portion comprises an intermediate median particle size in a range of 0.5- 1.5 pm and the activator second pozzolan portion comprises a coarse median particle size in a range of 10-80 pm.

10. The concrete composition of any of the preceding claims, further comprising a reinforcing material and a corrosion inhibitor selected from the group consisting of passivating agents, chloride scavengers, cathodic inhibitors, anodic inhibitors, oxidation inhibitors, electrochemical inhibitors, nitrite-based inhibitors, organic inhibitors, silane / siloxane treatments, galvanic protection systems, and polymeric barrier coatings.

11. The concrete composition of any of the preceding claims wherein the Dv50 of the activator admixture is less than 50pm.

12. The concrete composition of any of the preceding claims, wherein the activator pozzolan component exhibits a first volume density peak of between 0.3 and 1.5% for particles at between 0.5 pm and 1.5 pm and a second volume density peak of greater than 3% between 10 pm and 80 pm.

13. The concrete composition of any of the preceding claims, wherein the activator particle size distribution is defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm.

14. The concrete composition of any of the preceding claims, wherein the at least two pozzolan portions comprises at least about 60% by weight of the activator admixture.

15. The concrete composition of any of the preceding claims, wherein the activator admixture comprises a plasticiser, and the ratio between the activator pozzolan component and the plasticiser comprises from about 11:1 pozzolan: plasticiser to about 1.5:1 pozzolan: plasticiser.

16. The concrete composition of any of the preceding claims, wherein the activator comprises a plasticiser at between about 8% and 40% w / w.

17. The concrete composition of claim 16, wherein the plasticiser comprises a Dv50 of from 50-500 pm or 100-200 pm.

18. The concrete composition of any of the preceding claims, wherein the activator comprises a plasticiser selected from the group consisting of a polycarboxylate plasticiser; a naphthalene plasticiser, a superplasticiser; a lignosulphonate plasticiser; a dry form plasticiser; and a dry powder polycarboxylate superplasticiser.

19. The concrete composition of any of the preceding claims, wherein the activator is present in an amount of from 0.25-10% by weight of cementitious materials in the concrete composition.

20. The concrete composition of any of the preceding claims, wherein the activator is optionally present in an amount of from 0.5-8% by weight of cementitious materials in the concrete composition.

21. The concrete composition of any of the preceding claims, wherein the activator is optionally present in an amount of from 1-4% by weight of cementitious materials in the concrete composition.

22. The concrete composition of any of the preceding claims wherein the pozzolan portions comprise pozzolans selected from the group consisting of fly ash, slag, silica fume, metakaolin (thermally activated kaolin clay), rice husk ash, volcanic ash,pumice, calcium montmorrillonite clay, kaolinite, attapulgite, zeolite, silica, volcanic tuffs, pumice, pumicites, opaline cherts and shales, clays, and diatomaceous earth.

23. The concrete composition of any of the preceding claims, wherein the cementitious materials comprise Portland cement and at least one pozzolanic supplementary cementitious material (SCM) selected from the group consisting of fly ash, slag, silica fume, metakaolin, rice husk ash, synthetic pozzolan, natural pozzolan and pumice.

24. The concrete composition of claim 23, wherein the pozzolanic SCM is present in an amount of 10 to 50% w / w of cementitious material.

25. The concrete composition of claim 23 or 24, wherein limestone is present in an amount of 10 to 100% w / w of pozzolanic SCM.

26. The concrete composition of any of the preceding claims, wherein the composition comprises cementitious material comprising Portland cement at a quantity selected from the group consisting of less than 50%, less than 60%, less than 70%, less than 80%, or less than 90% Portland cement.

27. The concrete composition of any of the preceding claims wherein the activator admixture pozzolan component comprises two or more natural or synthetic pozzolans wherein the chemical composition of the two or more pozzolans differs in the amount of either silicon dioxide or aluminium oxide of at least 5% w / w.

28. The concrete composition of any of the preceding claims, wherein the compressive strength determined in accordance with NZS 3112 Part 2 at day 28 is greater than 20 MPa, optionally 25MPa, optionally 30MPa.

29. The concrete composition of any of the preceding claims, wherein the Dv50 of the second pozzolan portion is at least 2 times, optionally 4 times, 6 times or 10 times the Dv50 of the first pozzolan portion.

30. The concrete composition of any of the preceding claims, wherein the absolute difference between the Dv50 of the first and second pozzolan portions is at least 10 pm, optionally at least 20 pm, at least 30 pm, or at least 50 pm.

31. The concrete composition of any of the preceding claims, wherein the cementitious material comprises fly ash in an amount of 10-50% by weight of the cementitious material.

32. The concrete composition of any of the preceding claims, wherein both fly ash and limestone are present in the composition, each in an amount of at least 10% by weight of the cementitious material.

33. The concrete composition of any of the preceding claims, wherein the cementitious material comprises a natural pozzolan in an amount of 10-50% by weight of the cementitious material.

34. A concrete structure comprising the concrete composition of any one of claims 1 to 33.

35. A method of producing a limestone concrete composition comprising:a. obtaining a first pozzolan portion having a first chemical composition and a first median particle size, and a second pozzolan portion having a second chemical composition and a second median particle size;b. combining the first and second pozzolan portions to form a pozzolan component; andc. combining cementitious material, limestone, water, and an activator admixture comprising the pozzolan component and a plasticiser to form the limestone concrete composition,wherein the first and second pozzolan portions comprise different median particle sizes and / or different chemical compositions.

36. A method of producing a concrete composition comprising the steps of:a. obtaining a first pozzolan portion with a first chemical composition and a first median particle size, and a second pozzolan portion with a second chemical composition and second median particle size;b. combining the first pozzolan portion with the second pozzolan portion to form a pozzolan component;c. mixing the pozzolan component with a plasticiser to produce an activator admixture composition;d. combining the activator admixture composition with cementitious material and limestone;e. wherein the pozzolan component comprises a chemical composition comprising 20-80% w / w silicon dioxide and 5-40% aluminium oxide.

37. The method of claim 35 or 36, wherein the pozzolan component and plasticiser are pre-mixed prior to addition to the cementitious material and limestone.

38. The method of claim 35 or 36, wherein the pozzolan component and plasticiser are combined in situ during mixing of the cementitious material and limestone.

39. A method as claimed in claim 35 or 36, wherein the activator comprises an electrostatic charge.

40. A method as claimed in claim 37, wherein the electrostatic charge is applied to the activator by way of external electrical fields generated by electrodes, electrostatic spraying techniques, triboelectric charging in a fluidised bed, corona discharge methods, electrostatic fluidisation, and mechanical mixing-induced friction.

41. A method as claimed in any of claims 35 to 40, wherein the activator comprises a particle size distribution defined by:a. 15-55% of particles are less than 15 pm;b. 50-80% of particles are less than 40 pm; andc. 70-100% of particles are less than 90 pm.

42. The method of any of claims 35 to 41, wherein the concrete composition develops a compressive strength of at least 25 MPa at 28 days and comprises at least 10% by weight of natural or synthetic pozzolan SCM.

43. The method of any of claims 35 to 42, wherein the concrete composition, activator admixture or plasticiser are as described in any of claims 1 to 33.

44. The method of any of claims 35 to 43, further comprising forming the activator admixture by combining the pozzolan component with the plasticiser prior to addition of the activator admixture to the cementitious material and limestone.

45. The method of claim 44, wherein the activator admixture is fully prepared prior to contact with the cementitious material.

46. The method of any of claims 35 to 45, wherein the activator admixture is first combined with limestone prior to addition of cementitious material and water.

47. The method of any of claims 35 to 46, wherein the activator admixture is dry blended with limestone to form a pre-treated limestone component prior to addition of cementitious material.

48. The method of any of claims 35 to 47, wherein the activator admixture is first combined with the cementitious material prior to addition of limestone.

49. The method of any of claims 35 to 48, wherein the activator admixture is combined with one or more supplementary cementitious materials prior to addition of limestone and water.

50. A method of increasing limestone reactivity in a limestone concrete composition comprising limestone and cementitious material, the method comprising adding an activator admixture as defined in any one of claims 1 to 33 to the cementitious material and limestone.

51. The method of claim 50, wherein the method promotes formation of calcium-silicate- hydrate and / or carboaluminate hydration phases.

52. The method of claim 50 or 51, wherein the limestone is present at 5-30% by weight of the cementitious material.

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